scholarly journals Alkaline ribonuclease and ribonuclease inhibitor in mammary gland during the lactation cycle and in the R3230AC mammary tumour

1975 ◽  
Vol 148 (1) ◽  
pp. 67-76 ◽  
Author(s):  
D K Liu ◽  
G H Williams ◽  
P J Fritz
Keyword(s):  
Mammary Gland ◽  
Cell Number ◽  
Mammary Tumour ◽  
Ribonuclease Inhibitor ◽  
Cytosol Fraction ◽  
Pregnancy And Lactation ◽  
Alkaline Ribonuclease ◽  
Rat Mammary Gland ◽  
Lactation Cycle ◽  
Triton X

Alkaline RNAase (ribonuclease) and RNAase inhibitor were assayed to determine the potential role of the degradative process in regulating the amount of RNA in the mammary gland and mammary tumour. Very little free alkaline RNAase activity was found in the cytosol fraction of the mammary gland of virgin, pregnant, lactating or involuting Fischer rats. However, addition of p-chloromercuribenzoate to the assay medium revealed latent RNAase which, when expressed on a DNA basis, decreased during pregnancy and lactation. The cytosol latent RNAase is stable in 0.125 M-H2SO4. The non-cytosol RNAase activity also decreased during pregnancy and lactation. Addition of Triton X-100 produced slightly higher activity at all stages tested. The inhibitor activity in rat mammary gland was very low before pregnancy, increased gradually during pregnancy and more dramatically at parturition, continued to increase throughout lactation and returned to resting-gland values by the sixth day of involution. The increase during pregnancy may be due to the increased cellularity of the gland, whereas the gain during lactation was more than could be accounted for by increases in cell number. The R3230AC transplantable mammary tumour resembles the normal gland in early lactation with respect to both its cytosol and non-cytosol alkaline RNAase activities and its moderately high content of RNAase inhibitor. The relatively high inhibitor and low RNAase activities in both the gland of the lactating rat and in the tumour are of potential significance in maintaining high amounts of RNA and increased rates of protein synthesis in these tissues.

scholarly journals Phosphoribosyl pyrophosphate and phosphoribosyl pyrophosphate synthetase in rat mammary gland. Changes in the lactation cycle and effects of diabetes, insulin and phenazine methosulphate

1986 ◽  
Vol 238 (2) ◽  
pp. 553-559 ◽  
Author(s):  
S Kunjara ◽  
M Sochor ◽  
N Salih ◽  
P McLean ◽  
A L Greenbaum
Keyword(s):  
Mammary Gland ◽  
Fold Increase ◽  
Pentose Phosphate ◽  
Diabetic Rat ◽  
Synthetase Activity ◽  
Phosphoribosyl Pyrophosphate ◽  
Rat Mammary Gland ◽  
Lactation Cycle ◽  
Phenazine Methosulphate

Changes in the tissue content of phosphoribosyl pyrophosphate (PPRibP), glucose 6-phosphate, ribose 5-phosphate (Rib5P), RNA and DNA, of the activity of PPRibP synthetase (EC 2.7.6.1) and the conversion of [1-14C]- and [6-14C]-glucose into 14CO2 were measured at mid-lactation in the normal and diabetic rat and in pregnancy, lactation and mammary involution in the normal rat. The PPRibP, glucose 6-phosphate and Rib5P contents increase during pregnancy and early lactation to reach a plateau value at mid-lactation, before falling sharply during weaning. The PPRibP content, PPRibP synthetase activity and flux of glucose through the oxidative pentose phosphate pathway (PPP) all change in parallel during the lactation cycle. Similarly, after 3 and 5 days duration of streptozotocin-induced diabetes, ending on day 10 of lactation, there were parallel declines in PPRibP content, PPRibP synthetase and PPP activity. The effect of streptozotocin was prevented by pretreatment with nicotinamide and partially reversed by insulin administration. Addition of insulin to lactating rat mammary-gland slices incubated in vitro significantly raised the PPRibP content (+47%) and the activity of the PPP (+40%); phenazine methosulphate, which gives a 2-fold increase in PPP activity, raised the PPRibP content of lactating mammary gland slices by approx. 3-fold. It is concluded that Rib5P, generated in the oxidative segment of the PPP, is an important determinant of PPRibP synthesis in the lactating rat mammary gland and that insulin plays a central role in the regulation of the bioavailability of this precursor of nucleotide and nucleic acid synthesis.

β-Adrenergic Receptors in the Rat Mammary Gland during Pregnancy and Lactation: Characterization, Distribution, and Coupling to Adenylate Cyclase

Endocrinology ◽  
1990 ◽  
Vol 126 (1) ◽  
pp. 565-574 ◽  
Author(s):  
BIANCA MARCHETTI ◽  
MICHEL-A FORTIER ◽  
PATRICK POYET ◽  
NICOLLE FOLLEA ◽  
GEORGES PELLETIER ◽  
...  
Keyword(s):  
Mammary Gland ◽  
Adenylate Cyclase ◽  
Adrenergic Receptors ◽  
Pregnancy And Lactation ◽  
Rat Mammary Gland ◽  
Β Adrenergic Receptors

scholarly journals Enzymic changes in rabbit and rat mammary gland during the lactation cycle

1969 ◽  
Vol 112 (3) ◽  
pp. 293-301 ◽  
Author(s):  
Bilquis Gul ◽  
R. Dils
Keyword(s):  
Mammary Gland ◽  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Acid Synthesis ◽  
Mitochondrial Fraction ◽  
Soluble Form ◽  
Supernatant Fraction ◽  
Rat Mammary Gland ◽  
Lactation Cycle

1. Activities of glucose 6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), isocitrate dehydrogenase (EC 1.1.1.42), malate dehydrogenase (EC 1.1.1.37), malate dehydrogenase (decarboxylating) (EC 1.1.1.40), and pyruvate carboxylase (EC 6.4.1.1) were determined in subcellular fractions of mammary gland from rabbits during pregnancy, at different stages of lactation and during weaning. The results were compared with those obtained in similar experiments with rat mammary gland. 2. Three bases of expression of the activity of enzymes in the particle-free supernatant fraction of mammary gland were compared. During lactation, activity expressed per mg. of particle-free supernatant protein (uncorrected for milk protein) correlated well with that expressed per μg. of DNA phosphorus. The disadvantages of expressing activities per g. wet wt. are discussed. 3. The major differences between the two tissues were: (a) neither malate dehydrogenase (decarboxylating) nor a soluble form of pyruvate carboxylase could be detected in rabbit mammary gland at any stage of the lactation cycle; (b) isocitrate dehydrogenase increased in activity during lactation in rabbit mammary gland, but not in that of the rat. 4. Pyruvate carboxylase in the mitochondrial fraction of rabbit mammary gland, and in both the mitochondrial and the soluble fractions of rat mammary gland, did not change in activity during lactation. 5. For each tissue, the NADP-dependent dehydrogenases studied had a high activity at all stages of the lactation cycle compared with the rate of fatty acid synthesis at mid-lactation. The significance of these results is discussed with respect to the supply of NADPH via NADH.

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