IS PROLACTIN A GONADOTROPIC HORMONE IN RED DEER (CERVUS-ELAPHUS) - PATTERN OF EXPRESSION OF THE PROLACTIN RECEPTOR GENE IN THE TESTIS AND EPIDIDYMIS

This study investigated the pattern and site of expression of the prol actin receptor gene in the testis and epididymis of red deer collected during the breeding season (n=3). Ribonuclease protection assays usin g 50 mu g total RNA and a 300bp [P-32]-labelled antisense cRNA probe, generated from the extracellular domain of the red deer prolactin rece ptor, confirmed the expression of the receptor in both the testis and epididymis; a higher level of prolactin receptor mRNA was detected in the epididymis compared with the testis (170.4 +/- 1.5 x 10(3) and 26. 3 +/- 2.7 x 10(3) arbitrary units respectively; P<0.05). In situ hybri disation using 300bp [P-33]-labelled sense and antisense cRNA probes g enerated from the extracellular domain of the receptor localised the e xpression sites to the seminiferous tubules and interstitial compartme nts of the testis and the epithelial layer of the epididymal duct. Qua ntification of grain numbers demonstrated a higher level of expression of the receptor in the epididymis compared with the interstitial and seminiferous tubule compartments of the testis (18.1 +/- 4.4 x 10(2), 10.1 +/- 2.0 x 10(2) and 8.3 +/- 0.8 x 10(2) grains/mu m(2) respective ly; P<0.05). However, no differences mere detected in the level of exp ression of the receptor between the interstitial and seminiferous tubu le compartments of the testis. Immunocytochemistry using an anti-prola ctin receptor antibody, raised against a peptide sequence from the ext racellular domain of the rat prolactin receptor, localised expression of the receptor gene to the Leydig cells, pachytene spermatocytes, rou nd spermatids and elongating spermatids. In the epididymis, the recept or was localised to the epithelial layer within the epididymal ducts. Expression of the prolactin receptor gene in the red deer testis and e pididymis suggests a role for the hormone in steroidogenesis and sperm atogenesis.