Biol Reprod 2009 SSR Annual Meeting Abstracts
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Biology of Reproduction, Vol 39, 489-498, Copyright © 1988 by Society for the Study of Reproduction

ARTICLES

Pineal and pituitary involvement in the photoperiodic regulation of body weight, coat color and testicular size of the Djungarian hamster, Phodopus sungorus

P Niklowitz and K Hoffmann
Max Planck Clinical Research Unit for Reproductive Medicine, University of Munster, Federal Republic of Germany.

Hypophysectomy of 40-day-old male hamsters kept under long photoperiods resulted in a change in coat color from the brownish summer coat to the whitish winter coat, within 5 wk of the surgery, cessation of growth, and, most frequently, an additional loss in body weight. The testes of the hypophysectomized animals were involuted within 14 days after surgery. Continuous substitution of prolactin by implantation of two anterior pituitaries under the kidney capsule was able to reverse partly or totally the inhibitory effects of hypophysectomy on coat color and body weight, although there was no influence on testicular volume. The same effects could be achieved by daily s.c. injections of prolactin (100 micrograms ovine-PRL/day) into hypophysectomized hamsters, whereas the injection of adrenocorticopropic hormone (5 IU porcine-ACTH/day) or melanocyte-stimulating hormone (35 micrograms synthetic alpha-MSH/day) was ineffective. Additional pinealectomy influenced neither the inhibitory effects of hypophysectomy on coat pigmentation and body weight nor the stimulatory effects of prolactin substitution in hypophysectomized animals. Thus, the study provides evidence that the effects of the pineal gland on annual changes in body weight and coat color are mediated via the pituitary.


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Copyright © 1988 by the Society for the Study of Reproduction.