Effects of bromocriptine on pituitary and adrenal cortex in pre-adrenarchal rabbits

The effect of bromocriptine on the morphological picture and steroid content of the adrenal gland, and on certain pro-opiomelanocortin (C) peptides in the pituitary gland was evaluated in preadrenarchal rabbits. Eighteen immature male rabbits (5 weeks of age), were treated for 10 days with saline (n = 10,2 ml sc) or bromocriptine mesylate (n = 8, 3 mg/kg sc) two times/day. After the last administration all animals received dexamethasone (0.25 mg im) and the next morning, 60 min after ACTH injection (0.25 mg im), plasma was drawn and they were sacrificed. Adrenals and pituitaries were immediately removed. For each animal, one adrenal gland was fixed, dehydrated and embedded in paraffin for histology; the other one was stored in saline for determination of androstenedione (A), dehydroepiandrosterone (DHA), 17-OH progesterone (17 P), and cortisol. Steroids were analyzed by RIA after previous extraction and celite-ethyleneglycol chromatography, or directly (cortisol). The immunoreactivities (ir) related to beta-Endorphin (B-EP), ACTH and alpha-MSH were evaluated in pituitary homogenates using specific RIAs. The bromocriptine-treated rabbits showed a significant increase in the percentage of the adrenal zona reticularis (21.5 +/- 3.9% of total cortex vs. 12.7 +/- 1.3% in controls, p less than 0.05, mean +/- SE), and a decrease of the zona fasciculata (57.6 +/- 3.13% vs. 67.7 +/- 2.05% in controls, p less than 0.05). No significant changes were observed in the relative percentage of the zona glomerulosa.(ABSTRACT TRUNCATED AT 250 WORDS)