Abstract: 16

THE ROLE OF PROLACTIN IN TESTICULAR RECRUDESCENCE IN THE BLACK BEAR.

Lesley Howell-Skalla^{1 *}, Ralph Nelson² , Janice Bahr^{1 *}
Department of Animal Sciences, University of Illinois, Urbana, IL 61801 ¹
Department of Medicine, University of Illinois and Carle Hospital, Urbana, IL 61801 ²

The black bear is a seasonal breeder with a yearly cycle of prolactin (PRL) secretion that increases during long days coincident with testicular recrudescence. We hypothesized that in the black bear increasing serum concentrations of PRL associated with increasing day length promote testicular recrudescence by stimulating steroidogenesis. To test this hypothesis, we used a long-acting form of bromocriptine, Parlodel LAR, to suppress endogenous PRL during testicular recrudescence. Nine mature male black bears were housed in indoor/outdoor enclosures and exposed to natural day length. Four bears were treated with 100-150 mg Parlodel LAR once monthly from January-April whereas 5 bears served as controls. Serum samples and testicular measurements were obtained once monthly from January-May to determine serum concentrations of LH, PRL, and testosterone (T) and testicular size. Testicular biopsies were obtained in January, March, and May and analyzed for LH-, FSH-, and PRL- receptor mRNA abundance using reverse transcriptase-competitive polymerase chain reaction. Parlodel LAR prevented the increase in serum PRL concentrations that occurs during the lengthening days of spring. Suppression of serum PRL concentrations during testicular recrudescence yielded 3 major results: 1) prevented the increase in testicular LH- and PRL-receptor mRNA abundance observed in control bears in March; 2) lowered serum T concentrations in March and April; and 3) reduced testis size in May. We conclude that PRL has a key role in testicular recrudescence in the male black bear possibly by increasing testicular LH and PRL receptors thus making the testes more responsive to LH stimulation.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.