Premium
The influence of sex steroids on calcium‐ and magnesium‐induced mitogenesis in isolated rat thymic lymphocytes
Author(s) -
Morganand J. I.,
Perris A. D.
Publication year - 1974
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1040830216
Subject(s) - medicine , endocrinology , calcium , parathyroid hormone , cyclase , phosphodiesterase , calcitonin , adenylate kinase , biology , phosphodiesterase inhibitor , adenosine , chemistry , enzyme , biochemistry , stimulation , receptor
Elevated calcium and magnesium concentrations promoted mitotic activity in rat thymic lymphocyte cultures. Oestradiol inhibited calcium‐ but not magnesium‐induced mitogenesis. One prerequisite for the mitogenic action of calcium is a raised intracellular concentration of cyclic adenosine 3′5′ monophosphate (cyclic AMP) but cyclic AMP‐induced mitogenesis was insensitive to oestradiol. This suggests that the steroid blocks the mitogenic process at a stage preceding the endogenous cyclic AMP elevation. Furthermore the mitogenic actions of adrenaline, which stimulates adenylate cyclase (the enzyme responsible for cyclic AMP biosynthesis), and caffeine, which inhibits phosphodiesterase (the enzyme which degrades cyclic AMP) were also insensitive to oestradiol inhibition. This precludes a direct effect of the steroid on these enzymes. However, oestradiol did inhibit the mitogenic action of parathyroid hormone (PTH). Since the mitogenic action of PTH probably involves increased calcium entry to the cell, oestradiol may block this ion influx. The inhibition of calcium‐ and PTH‐induced mitogenesis must be attributable to some structurally specific action of oestradiol. The steroids cholesterol, progesterone and testosterone all failed to reduce calcium‐induced mitogenesis, whereas both α and β oestradiol were effective. In addition to its insensitivity to oestradiol inhibition, magnesium‐stimulated mitosis was unaffected by both imidazole and calcitonin at concentrations which significantly reduced calcium‐stimulated proliferation. These findings are compatible with the thesis that magnesium‐induced mitogenesis does not involve the elevation of cyclic AMP concentrations.