The Effects of 5-Hydroxytryptamine and Cyclic Amp on the Potential Profile across Isolated Salivary Glands

1972 ◽  
Vol 56 (2) ◽  
pp. 323-333
Author(s):  
WILLIAM T. PRINCE ◽  
MICHAEL J. BERRIDGE
Keyword(s):  
Salivary Gland ◽  
Membrane Potential ◽  
Cyclic Amp ◽  
Salivary Glands ◽  
Apical Membrane ◽  
Basal Membrane ◽  
Potential Profile ◽  
Step Potential ◽  
Bathing Medium ◽  
Transepithelial Potential

1. The sites of the transepithelial potential changes produced by 5-HT and cyclic AMP in the salivary gland of the blowfly (Calliphora) have been investigated. 2. Microelectrodes recorded a two-step potential profile across this epithelium. The cell was negative to both the bathing medium and the saliva. 3. The basal membrane potential was 44·0±0·2 mV and was affected very little by application of either 5-HT or cyclic AMP. 4. The apical membrane was depolarized by 5-HT and in contrast was hyperpolarized by cyclic AMP. 5. On the basis of these results it is concluded that 5-HT has two actions: (a) to stimulate a potassium pump on the apical membrane using cyclic AMP as an intermediary, (b) to increase chloride movement by a mechanism not directly involving cyclic AMP.

Studies on the mechanism of fluid secretion by isolated salivary glands of Calliphora

1976 ◽  
Vol 64 (2) ◽  
pp. 311-322
Author(s):  
M. J. Berridge ◽  
B. D. Lindley ◽  
W. T. Prince
Keyword(s):  
Salivary Glands ◽  
Apical Membrane ◽  
Potassium Concentration ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Major Cation ◽  
Diuretic Agent ◽  
External Potassium

1. Potassium is the major cation in the secretion of the salivary glands of Calliphora and is necessary for full secretory rates. 2. Other ions (rubidium and sodium) can support secretion in the absence of potassium. 39. During stimulation with 5-HT a Nernst plot of the basal membrane potential has a slope of 53 mV for a tenfold change in external potassium concentration and the slope at rest deviates from this over the range I-20 mM external potassium. 4. Hyperpolarization of the basal membrane by 5-HT is abolished if the chloride in the bathing medium is replaced by isethionate. 5. The diuretic agent amiloride inhibits fluid secretion by a mechanism which may include a reduction in calcium entry in addition to its recognized effect on sodium permeability. 6. A model is proposed in which fluid secretion is driven by the active transport of potassium across the apical membrane with chloride following passively.

The Role of Calcium in the Action of 5-Hydroxytryptamine and Cyclic Amp on Salivary Glands

1973 ◽  
Vol 58 (2) ◽  
pp. 367-384
Author(s):  
WILLIAM T. PRINCE ◽  
MICHAEL J. BERRIDGE
Keyword(s):  
Cyclic Amp ◽  
Salivary Glands ◽  
Normal Saline ◽  
Mode Of Action ◽  
Apical Membrane ◽  
Potential Response ◽  
Chloride Medium ◽  
Bathing Medium ◽  
Calcium Dependent

1. The role of calcium in the potential and secretory responses of isolated salivary glands of Calliphora to 5-HT and cyclic AMP has been studied. 2. Secretion induced by 5-HT was reversibly inhibited by removal of calcium from the bathing medium. 3. The chloride-dependent depolarization of the apical membrane produced by 5-HT was calcium dependent whereas the potential response to cyclic AMP was little effected. 4. Strontium and barium effectively substituted for calcium. 5. Manganese replaced calcium at the onset of secretory and potential responses but these responses were maintained when manganese was removed. 6. Lanthanum did not substitute for calcium in secretory responses but did inhibit the secretory and potential responses to calcium in calcium-depleted glands. 7. The rate of secretion in a low-chloride medium produced by cyclic AMP was significantly lower than that induced by 5-HT, but there was little difference in normal saline. 8. A model for the mode of action of 5-HT is proposed in which calcium acts as an intracellular intermediary controlling chloride movements whilst cyclic AMP controls a potassium pump.

Transepithelial and intracellular potentials in isolated Malpighian tubules of tenebrionid beetle

1987 ◽  
Vol 252 (4) ◽  
pp. F645-F653 ◽  
Author(s):  
S. W. Nicolson ◽  
L. C. Isaacson
Keyword(s):  
Membrane Potential ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Bathing Medium ◽  
Intracellular Potentials ◽  
Tenebrionid Beetle ◽  
Fold Reduction ◽  
K Concentration ◽  
Opposing Effects

Malpighian tubules of Onymacris plana (Coleoptera: Tenebrionidae) have been isolated for measurement of transepithelial and intracellular potentials, before and during stimulation of fluid secretion. In a bathing medium resembling the hemolymph composition of the insect, the transepithelial potential (VT) was approximately 13 mV, lumen positive. VT was subject to drift and frequently showed super-imposed regular oscillations, which were apparently action potentials associated with contractions of muscle fibers running along the tubules. Although tubules of Onymacris are approximately 8 cm long, the basal membrane potential (Vb) did not vary with distance along the tubule, averaging -31 mV. Addition of adenosine 3',5'-cyclic monophosphate (cAMP) or diuretic hormone (DH) homogenate to the bathing medium had no effect on Vb, but opposing effects on VT: cAMP caused it to increase to 60 mV, whereas DH homogenate caused a rapid drop in VT to almost zero. Ion substitutions in the bathing medium showed that under control conditions beetle tubules possessed appreciable basal permeability to both K and Cl ions, with a 10-fold reduction in bath K concentration hyperpolarizing Vb by 54 mV. The basal K and Cl channels were partially blocked by barium and thiocyanate ions, respectively. Stimulation with cAMP increased the apical membrane potential (Va) and significantly reduced the Cl permeability of the basal membrane, whereas its Na permeability remained negligible.

scholarly journals Secretion by the Malpighian tubules of Rhodnius prolixus stal: electrical events

1984 ◽  
Vol 110 (1) ◽  
pp. 275-290 ◽  
Author(s):  
M. J. O'Donnell ◽  
S. H. Maddrell
Keyword(s):  
Apical Membrane ◽  
Electrical Response ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Chloride Permeability ◽  
Bathing Medium ◽  
Before And After ◽  
Electrical Gradient ◽  
Cation Pump

Transepithelial and intracellular potentials have been simultaneously recorded from Rhodnius upper Malpighian tubules before and after stimulation of fluid secretion. The transepithelial electrical response to the diuretic hormone mimic 5-hydroxytryptamine (5-HT) was triphasic; recordings of intracellular potential changes indicated that the three phases represented successive events at the apical membrane. Depolarizations produced by increasing the bathing medium potassium concentration indicated that the basal membrane was much more permeable to potassium than to sodium. Electrical responses to chloride-free saline were inconsistent with a significant basal membrane chloride permeability. Chloride movements across the basal membrane were opposed by an electrical gradient of about 65 mV. The results of experiments in which tubules were exposed to chloride-free saline or sodium-free saline suggested that chloride entry into the cells was linked to the entry of Na+ and K+. The effects of furosemide and bumetanide upon secretion and potential changes suggested that chloride crossed the basal membrane through co-transport with Na+ and K+. Chloride probably crosses the apical membrane into the lumen passively in response to a favourable electrical gradient of about 35 mV. Cations must be actively pumped into the lumen against an electrical gradient of 35 mV. Our results support previous evidence for an apical cation pump which actively transports Na and K into the lumen. A tentative model of ionic movements during fluid secretion is presented. It is suggested that the apical cation pump maintains sodium at low intracellular concentrations, thereby maintaining a favourable gradient for entry of Na+ through the proposed basal co-transport step. The suggested stoichiometry is Na+:K+:2 Cl-.

scholarly journals Changes in apical [K+] produce delayed basal membrane responses of the retinal pigment epithelium in the gecko.

1984 ◽  
Vol 83 (2) ◽  
pp. 193-211 ◽  
Author(s):  
E R Griff ◽  
R H Steinberg
Keyword(s):  
Membrane Potential ◽  
Retinal Pigment Epithelium ◽  
Apical Membrane ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Basal Membrane ◽  
Subretinal Space ◽  
Bathing Solution ◽  
Subsequent Decrease ◽  
Opposite Sequence

We describe here a new retinal pigment epithelium (RPE) response, a delayed hyperpolarization of the RPE basal membrane, which is initiated by the light-evoked decrease of [K+]o in the subretinal space. This occurs in addition to an apical hyperpolarization previously described in cat (Steinberg et al., 1970; Schmidt and Steinberg, 1971) and in bullfrog (Oakley et al., 1977; Oakley, 1977). Intracellular and extracellular potentials and measurements of subretinal [K+]o were recorded from an in vitro preparation of neural retina-RPE-choroid from the lizard Gekko gekko in response to light. Extracellularly, the potential across the RPE, the transepithelial potential (TEP), first increased and then decreased during illumination. Whereas the light-evoked decrease in [K+]o predicted the increase in TEP, the subsequent decrease in TEP was greater than predicted by the reaccumulation of [K+]o. Intracellular RPE recordings showed that a delayed hyperpolarization generated at the RPE basal membrane produced the extra TEP decrease. At light offset, the opposite sequence of membrane potential changes occurred. RPE responses to changes in [K+]o were studied directly in the isolated gecko RPE-choroid. Decreasing [K+]o in the apical bathing solution produced first a hyperpolarization of the apical membrane, followed by a delayed hyperpolarization of the basal membrane, a sequence of membrane potential changes identical to those evoked by light. Increasing [K+]o produced the opposite sequence of membrane potential changes. In both preparations, the delayed basal membrane potentials were accompanied by changes in basal membrane conductance. The mechanism by which a change in extracellular [K+] outside the apical membrane leads to a polarization of the basal membrane remains to be determined.

Electrolyte transport by alkaline gland of little skate Raja erinacea

1985 ◽  
Vol 248 (3) ◽  
pp. R346-R352
Author(s):  
P. L. Smith
Keyword(s):  
Membrane Potential ◽  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Transepithelial Resistance ◽  
Bathing Solution ◽  
Raja Erinacea ◽  
Cl Secretion ◽  
Transepithelial Potential

Transepithelial flux studies and conventional intracellular microelectrode measurements were employed to examine the mechanisms of ion transport by the alkaline gland of the male skate, Raja erinacea. These studies reveal that the transepithelial potential is 6.9 +/- 0.6 mV, lumen reference, and that the transepithelial resistance is 140 omega . cm2. The short-circuit current across this epithelium is entirely accounted for by net secretion of Cl, whereas transepithelial active transport of Na does not appear to be present in this tissue. Cl secretion and/or short-circuit current are reduced by serosal furosemide and abolished when the bathing solution Na is replaced with choline or when ouabain is added to the serosal bathing solution. Intracellular microelectrode studies reveal that the apical membrane potential is -43 mV, cell interior negative to the mucosal bathing solution. The transepithelial resistance in these tissues was 103 +/- 12 omega . cm2 and the apparent fractional resistance, i.e., the ratio of the change in apical membrane potential to the change in transepithelial potential produced by passing current across the epithelium was 0.39 +/- 0.09. Ion substitution experiments demonstrated that the apical membrane is dominated by a large Cl conductance while the basolateral membrane contains a barium-sensitive potassium conductance. These results suggest that the mechanism of Cl secretion by the alkaline gland is similar to the mechanism described for a variety of Cl secretory epithelia.

scholarly journals Forskolin as an activator of cyclic AMP accumulation and secretion in blowfly salivary glands

1982 ◽  
Vol 204 (1) ◽  
pp. 147-151 ◽  
Author(s):  
I Litosch ◽  
Y Saito ◽  
J N Fain
Keyword(s):  
Salivary Gland ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Salivary Glands ◽  
Mammalian Cells ◽  
Salivary Secretion ◽  
Gland Secretion ◽  
Cyclic Amp Accumulation ◽  
Salivary Gland Secretion ◽  
Stimulation Of

Forskolin is a diterpene that activates adenylate cyclase in a variety of mammalian cells. In addition of forskolin to blowfly salivary glands increased cyclic AMP accumulation and salivary secretion. There was a small increase in transepithelial movement of labelled Ca2+. Forskolin did not induce breakdown of labelled phosphatidylinositol or inhibit the stimulation of phosphatidylinositol breakdown caused by 5-hydroxytryptamine. These data indicate that forskolin can mimic all the effects of 5-hydroxytryptamine on salivary-gland secretion that have been attributed to cyclic AMP.

scholarly journals Cellular mechanisms and control of KCl absorption in insect hindgut

1983 ◽  
Vol 106 (1) ◽  
pp. 71-89 ◽  
Author(s):  
J. W. Hanrahan ◽  
J. E. Phillips
Keyword(s):  
Cyclic Amp ◽  
Apical Membrane ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Basal Membrane ◽  
Peptide Hormone ◽  
Open Circuit ◽  
Electrochemical Gradient ◽  
Cellular Mechanisms

The hindgut of the desert locust possesses an unusual chloride transport system. The isolated locust rectum absorbs chloride from the mucosal (lumen) to the serosal (haemolymph) side at a rate which is equal to the short-circuit current (Isc). Net chloride transport (JClnet) persists in nominally Na-free or HCO3(CO2)-free saline, is insensitive to normal inhibitors of NaCl co-transport and anion exchange, and is independent of the net electrochemical gradient for sodium across the apical membrane. However, active chloride transport is strongly dependent on mucosal potassium (Ka = 5.3 mM-K). Chloride entry across the apical membrane is active, whereas the net electrochemical gradient across the apical membrane is active, whereas the net electrochemical gradient across the basal membrane favours passive Cl exit from the cell. Although mucosal potassium directly stimulates ‘uphill’ chloride entry, there is no evidence for coupled KCl co-transport, nor would co-entry with potassium be advantageous energetically. Net chloride absorption and Isc are stimulated by a peptide hormone from the central nervous system which acts via cyclic-AMP. Cyclic-AMP increases Isc and JClnet approximately 1000% and transepithelial conductance (Gt) approximately 100%. Approximately half of the delta Gt during stimulation results from increased Cl conductance at the basal cell border. This increase is also reflected in a shift of the basal membrane e.m.f. towards the Nernst potential for chloride. The remainder of the cAMP-induced delta Gt is due to an elevation of apical membrane K conductance, which causes a 400% increase in transepithelial potassium permeability as estimated by radiotracer diffusion. Because of this stimulation of K conductance, potassium serves as the principal counterion for active chloride transport under open-circuit conditions. Very high luminal levels of K oppose the stimulatory actions of cAMP on active Cl transport and K conductance. These and other results have been incorporated into a cellular model for KCl absorption across this insect epithelium.

The electrical response of isolated salivary glands during stimulation with 5-hydroxytryptamine and cyclic AMP

1971 ◽  
Vol 262 (842) ◽  
pp. 111-120 ◽  
Keyword(s):  
Cyclic Amp ◽  
Salivary Glands ◽  
Electrical Response ◽  
Liquid Paraffin ◽  
Fluid Secretion ◽  
Positive Potential ◽  
Bathing Medium ◽  
Gap Technique ◽  
Rapid Changes ◽  
Continuous Potential

Rate of fluid secretion by the salivary glands of the blowfly Calliphora is regulated by 5-hydroxytryptamine (5-HT) working in conjunction with cyclic AMP. Although cyclic AMP can exactly mimic the acceleration of fluid secretion produced by 5-HT, the underlying electrical events are completely different. Transepithelial potentials were measured by a liquid paraffin-gap technique which permits continuous potential recordings during rapid changes of the bathing medium. The potential of the lumen of unstimulated glands is + 5 mV with respect to the bathing medium but becomes — 10 to 20 mV after applying 5-HT. After stimulation with cyclic AMP, however, the luminal potential becomes more positive (+ 30 to 40 mV). A similar effect is obtained with theophylline or when glands are treated with 5-HT in the presence of an impermeant anion such as isethionate. These observations suggest that in addition to stimulating the synthesis of cyclic AMP, 5-HT may also act directly to increase anion movement. Cyclic AMP appears to stimulate cation transport, which explains the increase in positive potential obtained when this compound (or theophylline) is applied in the absence of 5-HT.

scholarly journals Mechanisms of K+ uptake across the basal membrane of malpighian tubules of Formica polyctena: the effect of ions and inhibitors.

1994 ◽  
Vol 195 (1) ◽  
pp. 123-145 ◽  
Author(s):  
A Leyssens ◽  
S Dijkstra ◽  
E Van Kerkhove ◽  
P Steels
Keyword(s):  
Membrane Potential ◽  
Electrical Potential ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
K Uptake ◽  
Bathing Medium ◽  
K Channels ◽  
High K ◽  
K Concentration

In the presence of 6 mmol l-1 Ba2+, known to block the K+ channels in the basal membrane, a rise in bath [K+] ([K+]bl) induced an increase in intracellular K+ concentration ([K+]i) similar in amount and in time course to that obtained in the absence of Ba2+. The presence of active and passive (other than through K+ channels) K+ uptake mechanisms across the basal membrane was investigated in different bath K+ concentrations. Dihydro-ouabain (10(-3) mol l-1), a blocker of the Na+/K(+)-ATPase, tested in low bath [K+], and Sch28080 (10(-4) mol l-1), a K+/H(+)-ATPase inhibitor, were without effect on fluid secretion. Dihydro-ouabain was also without effect on electrical potential differences either in the absence or in the presence of Ba2+. Vanadate (10(-3) mol l-1), in contrast, strongly reduced fluid secretion not only in control solution but also in high-K+, Na(+)-free medium and reduced the transepithelial and the apical membrane potential differences but not the basal membrane potential difference of [K+]i. Omitting Na+ from the bathing medium, replacing Cl- by Br- or applying bumetanide (10(-5) mol l-1) inhibited fluid secretion only in a low-K+ (10 mmol l-1) medium. In 51 mmol l-1 [K+]bl, omitting Na+ was without effect and 10(-4) mol l-1 bumetanide was needed to inhibit secretion. Replacing Cl- by Br- stimulated fluid secretion at this K+ concentration. Bumetanide (10(-4) mol l-1) had no effect in 113 mmol l-1 [K+]bl. Bumetanide (10(-4) mol l-1) in 51 mmol l-1 [K+]bl did not affect membrane potentials, did not lower [K+]i and did not affect the rise in [K+]i observed on an increase in [K+]bl. The results were summarized in a model proposing that K+ channels play a dominant role in high-K+ (113 mmol l-1) bathing medium. A K+/Cl- cotransporter may become more important in 51 mmol l-1 [K+]bl and a K+/Na+/2Cl- cotransporter may gain in importance in 10 mmol l-1 [K+]bl. Active mechanisms for K+ uptake across the basal membrane seem to play no detectable role in sustaining fluid secretion. The response to vanadate might be due to an effect on the apical electrogenic H+ pump.

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