ISSN:
0730-2312
Keywords:
poly(ADP-ribosyl)ation
;
mammary gland
;
histone H1
;
HMG proteins
;
prolactin
;
insulin
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Poly(adenosine diphosphate [ADP]-ribosyl)ation, although associated with differentiation in many systems, exhibited a reciprocal relationship with mammary gland differentiation, and both the synthetic and degradatory pathways complemented each other in this regard. Poly(ADP-ribosyl)synthetase activity declined during pregnancy and lactation, while poly(ADP-ribose) degradatory activity rose late in pregnancy and peaked during lactation. In explant cultures, similar changes occurred and appeared to be under separate hormonal control; prolactin suppressed the synthetase activity, whereas insulin stimulated the poly(ADP-ribosyl)glycohydrolase activity. This latter effect may be mediated by a decline in cAMP levels for the following reasons: the glycohydrolase is known to be inhibited by cAMP, insulin decreased cAMP concentrations in mammary explants by 70%, and cholera toxin blocked the effects of insulin on poly(ADP-ribose) degradation. This reciprocal relationship between poly(ADP-ribosyl)ation and mammary gland differentiation is further supported by pharmacological studies: in the presence of insulin, cortisol, and prolactin, an inhibitor of the synthetase stimulated α-lactalbumin three-fold over hormone stimulation alone. However, this inhibitor was unable to induce differentiation in the absence of prolactin. Therefore, although there is a close association between a decline in enzyme activity and mammary differentiation, the data are insufficient to support a causal relationship.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcb.240290409
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