Faculty Collaboration Database

Annual changes in serum concentrations of prolactin in captive male black bears (Ursus americanus). J Reprod Fertil 1995 Jul;104(2):187-91

Date

07/01/1995

Pubmed ID

7473406

DOI

10.1530/jrf.0.1040187

Scopus ID

2-s2.0-0029148585 (requires institutional sign-in at Scopus site)   11 Citations

Abstract

Prolactin may be involved in the regulation of reproduction in black bears (Ursus americanus) as it is a mediator of photoperiodic changes in a number of species. The objectives of this study were to validate a radioimmunoassay to measure prolactin in bear serum and to describe seasonal changes in serum prolactin concentrations in captive male bears. Serum samples were obtained nine times during a year from three captive male black bears that were denning between November and March and active during the other months. The heterologous prolactin radioimmunoassay, using pig 125I-labelled prolactin and goat anti-pig prolactin as a primary antibody, was validated. Injection of thyrotrophin-releasing hormone into the three male bears in June resulted in a rapid increase in serum concentrations of prolactin (t = 0, 11.4-14.8 ng ml-1; t = 15-30 min, 18.4-28.7 ng ml-1). The sensitivity of the assay was 0.08 ng per tube. Intra- and interassay coefficients of variation were 5.5% (n = 6) and 5.7% (n = 6), respectively. Serum concentrations of prolactin changed seasonally, with the lowest concentrations in December (mean +/- SD = 1.1 +/- 0.1 ng ml-1); this was followed by a gradual increase between January (2.6 +/- 0.6 ng ml-1) and April (6.4 +/- 1.2 ng ml-1) and the highest concentrations in May (17.6 +/- 4.7 ng ml-1), preceding peak testosterone concentrations in June. The observation that prolactin secretion increased with increasing daylength suggests that photoperiod may be an external regulator. The presence of high concentrations of prolactin before peak testosterone concentrations suggests that prolactin may play a role in regulating seasonal changes in the testes.

Author List

Tsubota T, Nelson RA, Thulin JD, Howell L, Bahr JM

Author

Joseph Thulin DVM Assistant Provost, Professor in the Research Office department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Male
Prolactin
Radioimmunoassay
Reproducibility of Results
Seasons
Testosterone
Thyrotropin
Ursidae