FSH AND LH STIMULATION OF ORNITHINE DECARBOXYLASE ACTIVITY: STUDIES WITH PORCINE GRANULOSA CELLS IN VITRO

We examined the role of Ca2+ in the control of basal and hormone-stimulated ornithine decarboxylase activity in isolated pig granulosa cells maintained under chemically defined conditions in vitro. Omission of Ca2+ from the incubation medium (measured Ca2+ concentration 5μm) decreased basal enzymic activity, and significantly (P<0.01) impaired the response to maximally stimulating doses of either lutropin or follitropin. No significant alteration occurred in the concentration of either gonadotropin required to elicit half-maximal effects. The addition of EGTA (1.27–2.0mm) to chelate residual extracellular Ca2+ further decreased hormone-induced rises in ornithine decarboxylase activity. Despite the presence of 1.27mm concentrations of extracellular Ca2+, the administration of presumptive Ca2+ antagonists, believed to impair trans-membrane Ca2+ influx [verapamil (10–100μm), nifedipine (1–100μm) or CoCl2 (1mm)] suppressed hormone-stimulated ornithine decarboxylase activity. The inhibitory effects of verapamil or of Ca2+ omission from the medium were not overcome by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0.25mm), or by cholera toxin, or by an exogenously supplied cyclic AMP analogue, 8-bromo cyclic AMP. Conversely, micromolar concentrations of a putative bivalent-cation ionophore, A23187, increased significantly the stimulation of ornithine decarboxylase activity by saturating concentrations of lutropin or 8-bromo cyclic AMP. Thus the present observations implicate Ca2+ ions in the modulation of hormone action and cellular function in normal ovarian cells.

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Stimulation of ornithine decarboxylase activity by luteinizing hormone in rat testicular interstitial cells in vitro is age dependent

Life Sciences ◽

10.1016/s0024-3205(83)80008-3 ◽

1983 ◽

Vol 33 (4) ◽

pp. 353-357 ◽

Cited By ~ 3

Author(s):

J. Osterman ◽

D. Barnett ◽

E.P. Murono ◽

T. Lin ◽

H.R. Nankin

Keyword(s):

Luteinizing Hormone ◽

Ornithine Decarboxylase ◽

Interstitial Cells ◽

Decarboxylase Activity ◽

Ornithine Decarboxylase Activity ◽

Age Dependent ◽

Testicular Interstitial Cells ◽

Stimulation Of

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Studies on regulatory factors of ornithine decarboxylase activity during development of mouse mammary epithelium in vitro.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(17)33711-0 ◽

1976 ◽

Vol 251 (6) ◽

pp. 1738-1744

Author(s):

T Oka ◽

J W Perry

Keyword(s):

Ornithine Decarboxylase ◽

Mammary Epithelium ◽

Decarboxylase Activity ◽

Regulatory Factors ◽

Ornithine Decarboxylase Activity ◽

Mouse Mammary Epithelium

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Role of pyridoxal phosphate in mammalian polyamine biosynthesis. Lack of requirement for mammalian S-adenosylmethionine decarboxylase activity

Biochemical Journal ◽

10.1042/bj1660081 ◽

1977 ◽

Vol 166 (1) ◽

pp. 81-88 ◽

Cited By ~ 19

Author(s):

A E Pegg

Keyword(s):

Ornithine Decarboxylase ◽

Pyridoxal Phosphate ◽

Vitamin B ◽

Decarboxylase Activity ◽

Deficient Diet ◽

Polyamine Biosynthesis ◽

Adenosylmethionine Decarboxylase ◽

Ornithine Decarboxylase Activity

1. Polyamine concentrations were decreased in rats fed on a diet deficient in vitamin B-6. 2. Ornithine decarboxylase activity was decreased by vitamin B-6 deficiency when assayed in tissue extracts without addition of pyridoxal phosphate, but was greater than in control extracts when pyridoxal phosphate was present in saturating amounts. 3. In contrast, the activity of S-adenosylmethionine decarboxylase was not enhanced by pyridoxal phosphate addition even when dialysed extracts were prepared from tissues of young rats suckled by mothers fed on the vitamin B-6-deficient diet. 4. S-Adenosylmethionine decarboxylase activities were increased by administration of methylglyoxal bis(guanylhydrazone) (1,1′-[(methylethanediylidine)dinitrilo]diguanidine) to similar extents in both control and vitamin B-6-deficient animals. 5. The spectrum of highly purified liver S-adenosylmethionine decarboxylase did not indicate the presence of pyridoxal phosphate. After inactivation of the enzyme by reaction with NaB3H4, radioactivity was incorporated into the enzyme, but was not present as a reduced derivative of pyridoxal phosphate. 6. It is concluded that the decreased concentrations of polyamines in rats fed on a diet containing vitamin B-6 may be due to decreased activity or ornithine decarboxylase or may be caused by an unknown mechanism responding to growth retardation produced by the vitamin deficiency. In either case, measurements of S-adenosylmethionine decarboxylase and ornithine decarboxylase activity under optimum conditions in vitro do not correlate with the polyamine concentrations in vivo.

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