Modification of Serum Luteinizing Hormone and Prolactin Concentrations by Corticotropin and Adrenalectomy in Ovariectomized Rats

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Abstract
The effects of ACTH and adrenalectomy (ADX) on serum concentrations of LH [luteinizing hormone] and prolactin were examined in ovariectomized (OVX) rats. In the 1st study ACTH (4 IU) was administered daily for 1 wk. ACTH prevented an increase in serum LH in response to OVX and stimulated serum prolactin. ACTH also reduced serum LH in OVX + ADX rats and increased prolactin concentration. ADX was utilized in the 2nd experiment to enhance secretion of endogenous ACTH. Two weeks after ADX serum prolactin was elevated above intact values. ADX also enhanced serum prolactin in OVX rats to the level found in intact animals. ADX markedly reduced the LH response to OVX but ADX alone had no effect on serum LH concentration. ACTH acts directly to reduce serum LH concentration and to enhance serum prolactin. The influence of adrenal corticoids on serum concentrations of LH and prolactin as reported by other investigators appears to be mediated via their negative feedback effects on ACTH release. Whether ACTH has its action on adenohypophyseal cells or on hypothalamic sites has yet to be determined.