Effects of parathyroid hormone and N6,O2?-dibutyryl cyclic AMP on Ca2+ transport across the rabbit distal nephron segments perfused in vitro

1981 ◽  
Vol 390 (2) ◽  
pp. 145-151 ◽  
Author(s):  
Masashi Imai
Keyword(s):  
Parathyroid Hormone ◽  
Cyclic Amp ◽  
Distal Nephron ◽  
Dibutyryl Cyclic Amp ◽  
Nephron Segments

Effects of PTH, calcitonin, and cAMP on calcium transport in rabbit distal nephron segments

1990 ◽  
Vol 259 (3) ◽  
pp. F408-F414 ◽  
Author(s):  
T. Shimizu ◽  
K. Yoshitomi ◽  
M. Nakamura ◽  
M. Imai
Keyword(s):  
Parathyroid Hormone ◽  
Adenylate Cyclase ◽  
Calcium Transport ◽  
Collecting Duct ◽  
Exchange Process ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Nephron Segments ◽  
Bathing Fluid

Distal nephron segments are heterogenous with respect to adenylate cyclase responses to stimulation with parathyroid hormone (PTH) or calcitonin (CT). We examined effects of these hormones and of 8-(p-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPTcAMP) on net Ca absorption (Jnet Ca2+, pmol.min-1.mm-1) in rabbit distal nephron segments by in vitro microperfusion technique. We studied three segments, including distal convoluted tubule (DCT), connecting tubule (CNT), and cortical collecting duct (CCD). PTH (1 nM) in bath significantly increased Jnet Ca2+ from 2.28 +/- 0.35 to 9.44 +/- 1.13 in CNT, but did not affect Jnet Ca2+ in DCT or CCD. CT (1 nM) in bath significantly increased Jnet Ca2+ from 1.58 +/- 0.29 to 4.45 +/- 1.01 in DCT, whereas it did not affect Jnet Ca2+ either in CNT or in CCD. CPTcAMP (30 microM) in bath significantly increased Jnet Ca2+ from 2.29 +/- 0.42 to 3.97 +/- 0.43 in DCT and from 2.43 +/- 0.18 to 5.83 +/- 0.37 in CNT, but it did not affect Jnet Ca2+ in CCD. When Na+ was removed from bathing fluid or when 0.1 mM ouabain was added to bath, Jnet Ca2+ in both DCT and CNT significantly decreased. Furthermore, stimulatory effects of PTH and CT on Ca2+ absorption in the respective segments were abolished under these conditions. These results suggest that PTH and CT increase Ca2+ absorption in CNT and DCT, respectively, through cAMP-mediated mechanisms. Presence of a basolateral Na(+)-Ca2+ exchange process seems to be a prerequisite for effects of these hormones. However, exact intracellular mechanisms remain uncertain.

PTH inhibition of bicarbonate transport by proximal convoluted tubules

1980 ◽  
Vol 239 (2) ◽  
pp. F127-F134 ◽  
Author(s):  
T. D. McKinney ◽  
P. Myers
Keyword(s):  
Parathyroid Hormone ◽  
Cyclic Amp ◽  
Co2 Concentration ◽  
Bicarbonate Transport ◽  
Co2 Absorption ◽  
Fluid Absorption ◽  
Dibutyryl Cyclic Amp ◽  
Convoluted Tubules ◽  
Proximal Convoluted Tubules

These studies examined the effect of parathyroid hormone (PTH), dibutyryl cyclic AMP DBcAMP, and 8-bromo-cyclic AMP BrcAMP on HCO3- transport by rabbit superficial proximal convoluted tubules perfused in vitro. Bicarbonate was estimated as total CO2 measured microcalorimetrically. At slow perfusion rates with 25 mM HCO3- in the perfusate and bath, PTH (0.1 U/ml in the bath) caused the total CO2 in tubular fluid to rise from 10.2 to 19.9 mM. The hormone had no effect on the total CO2 concentration in tubules perfused with HCO3(-)-free perfusates. With HCO3(-) in the perfusate and bath, PTH reduced the rates of fluid and total CO2 absorption to 57 and 48% of control values, respectively. PTH had no effect on the rates of fluid absorption and total CO2 secretion when HCO3(-)-free perfusates were used. The effects of DBcAMP and BrcAMP (10(-7) M in the bath) were similar to those of PTH. 5'-AMP (10(-6) M in the bath) did not alter the total CO2 concentration of tubular fluid when the tubules were perfused at slow rates with HCO3- in the perfusate and bath. Ouabain (10(-5) M in the bath) caused the total CO2 concentration in tubules perfused at slow rates with HCO3--free perfusates to rise from 8.9 to 12.7 mM. PTH caused no further change in the total CO2 concentration in the presence of ouabain.

The inhibitory effects of some adenosine nucleolipids on the lipolysis in rat epididymal fat pads in vitro

1979 ◽  
Vol 44 (5) ◽  
pp. 1651-1656 ◽  
Author(s):  
Sixtus Hynie ◽  
Jiří Smrt
Keyword(s):  
Fatty Acids ◽  
Cyclic Amp ◽  
Dibutyryl Cyclic Amp ◽  
Inhibitory Effects ◽  
Epididymal Fat ◽  
Fat Pads

3'-Oleolyl-2,3-dihydroxypropyl-AMP, 3'-stearoyl-2,3-dihydroxypropyl-AMP, octadecyl-AMP and palmitamidoethyl-AMP inhibited in comparison with adenosine or fatty acids much stronger the lipolysis in rat epididymal fat pads in vitro stimulated by isoproterenol, theophylline and dibutyryl cyclic AMP. The inhibition of the effects of the two latter drugs suggest that the described effect is caused not only by the inhibition of the cyclic AMP production but also by the inhibition of its effect on the following steps in process of lipolysis.

TESTOSTERONE SECRETION BY FOETAL RAT TESTES IN VITRO

1976 ◽  
Vol 71 (2) ◽  
pp. 231-238 ◽  
Author(s):  
RÉGINE PICON
Keyword(s):  
Cyclic Amp ◽  
Synthetic Medium ◽  
Functional Differentiation ◽  
Dibutyryl Cyclic Amp ◽  
Testosterone Secretion ◽  
Testosterone Production ◽  
Foetal Rat

SUMMARY Testosterone secretion by foetal rat testes (13½–21½ days of gestation) explanted for 3 days in a synthetic medium was measured every 24 h by radioimmunoassay. During the first day of explantation, the foetal testis produced, respectively, 1013 ± 132, 8734 ± 1118, 9179 ± 2185 and 3886 ± 309 (s.e.m.) pg/testis when explanted at 14½, 16½, 18½ and 21½ days respectively. Testosterone production by 13½-day-old testes was not detectable on the first day of culture, but appeared on subsequent days. Daily testosterone secretion increased on the 2nd and 3rd days of culture in 14½-day-old testes and decreased in older stages. These results suggest that the functional differentiation of the testis is independent of stimulatory factors like gonadotrophins. Dibutyryl cyclic AMP was found to stimulate testosterone production significantly from 14½ days of gestation onwards.

scholarly journals Influence of A23187 and dibutyryl cyclic AMP on progestagen production by rat granulosa cells in vitro

Reproduction ◽  
1989 ◽  
Vol 86 (1) ◽  
pp. 373-381 ◽  
Author(s):  
B. K. Tsang ◽  
D. F. Mattice ◽  
M. Li ◽  
E. K. Asem
Keyword(s):  
Cyclic Amp ◽  
Granulosa Cells ◽  
Dibutyryl Cyclic Amp

scholarly journals Isolation of cDNA clones for genes exhibiting reduced expression after differentiation of murine teratocarcinoma stem cells.

1984 ◽  
Vol 4 (10) ◽  
pp. 2142-2150 ◽  
Author(s):  
R A Levine ◽  
G J LaRosa ◽  
L J Gudas
Keyword(s):  
Stem Cells ◽  
Retinoic Acid ◽  
Cyclic Amp ◽  
Cdna Library ◽  
In Vitro Transcription ◽  
In Vitro Translation ◽  
Transcriptional Level ◽  
Cdna Clones ◽  
Dibutyryl Cyclic Amp

In the absence of retinoic acid, PSA-G teratocarcinoma stem cells spontaneously differentiate at a moderate frequency into fibroblast-like cells. In the presence of retinoic acid and dibutyryl cyclic AMP, PSA-G stem cells differentiate into parietal endoderm cells. We prepared a cDNA library from undifferentiated PSA-G teratocarcinoma stem cells; this cDNA library was then screened for gene sequences which exhibit a reduction in expression during the differentiation of these stem cells. From ca. 1,000 clones screened, eight independent sequences were isolated. The level of expression of these cloned genes decreases by 3.0-fold to more than 10-fold after differentiation of PSA-G cells into fibroblast-like cells. After treatment of either PSA-G or F9 teratocarcinoma cells with retinoic acid and dibutyryl cyclic AMP for 72 h, the expression of seven genes is inhibited by two- to fourfold. This decrease of clone-specific transcripts can be detected within 12 h after the addition of retinoic acid. Hybridization-selection and in vitro translation experiments identified the proteins encoded by three of the cloned genes: pST 6-23 codes for a 89,000-dalton protein, pST 7-105 codes for a 41,000-dalton protein, and pST 9-31 codes for a 34,000-dalton protein. The 89,000-dalton protein encoded by pST 6-23 is a heat shock protein. In vitro transcription experiments demonstrate that the retinoic acid-mediated decrease in pST 6-135- and pST 1-68-specific RNA occurs at the transcriptional level and that dibutyryl cyclic AMP acts posttranscriptionally to further depress the levels of these RNAs.

Stimulation of aromatase activity in the fetal rat testis by cyclic AMP and FSH

1988 ◽  
Vol 118 (3) ◽  
pp. 485-489 ◽  
Author(s):  
J.-P. Weniger ◽  
A. Zeis
Keyword(s):  
Cyclic Amp ◽  
Specific Activity ◽  
Isotopic Dilution ◽  
Aromatase Activity ◽  
Dibutyryl Cyclic Amp ◽  
Rat Testis ◽  
Fetal Rat ◽  
Fetal Rats ◽  
Stimulation Of

ABSTRACT The effect of dibutyryl cyclic AMP and FSH on oestrogen biosynthesis was investigated in testes from 18- to 21-day-old fetal rats cultured in vitro in the presence of tritiated testosterone. Oestrone and oestradiol concentrations were measured by determination of constant specific activity after isotopic dilution. Dibutyryl cyclic AMP and FSH markedly stimulated the conversion of testosterone into both oestrone and oestradiol at all stages studied. Oestradiol synthesis was stimulated by two- to sevenfold, while stimulation of oestrone synthesis was even greater. The results demonstrate that the aromatase enzyme system of the fetal rat testis responds to cyclic AMP and FSH. J. Endocr. (1988) 118, 485–489

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