Title: IDENTIFICATION OF MAMMOSOMATOTROPHS IN THE TURKEY HEN PITUITARY: INCREASED ABUDANCE DURING HYPERPROLACTINEMIA
Ramesh, R - UNIVERSITY OF MARYLAND
Solow, R - USDA, ARS, LPSI, GGPL
Kuenzel, W - UNIVERSITY OF MARYLAND
Submitted to: Journal of Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 1997
Publication Date: N/A
Interpretive Summary: The pituitary gland hormones, which regulate many vital body functions,are each produced by specialized cells. It has been shown in mammals that pituitary cell function can change in the adult animal from production of one hormone (growth hormone; GH) to production of a different hormone (prolactin; PRL) when PRL is required for reproduction. This change occurs, at least in part, through an intermediate cell (mammosomatotroph) that contains both hormones. Since the turkey hen undergoes a dramatic increase in PRL secretion during the change from egg-laying to incubation behavior, the present study was conducted to determine if mammosomatotrophs occur in the turkey pituitary, and if the presence of these cells changes with reproduction. Staining of pituitary cells for GH and PRL showed that mammosomatotrophs are present in both laying and incubating turkey hens, and that the abundance of these cells is increased nearly 5-fold in the incubating hen. Detection of PRL messenger RNA in cells containing GH confirmed that PRL was synthesized in these cells. These results show that the increased PRL secretion that causes incubation behavior and loss of egg production in the turkey is associated with a change pituitary cell function. This information will be used by scientists to identify the genes or physiological signals which cause this behavioral change.
We have previously reported that the hyperprolactinemia in incubating turkey hens is associated with recruitment of lactotrophs in the pituitary gland. In this study, we have used double immunofluorescence and in situ hybridization histochemistry to (i) identify mammosomatotrophs in the anterior pituitary gland of egg laying turkey hens and incubating hens, and d(ii) to verify prolactin (PRL) synthesis within mammosomatotrophs by co- localizing PRL mRNBA in growth hormone (GH)-immunoreactive (ir) cells. The pituitaries of laying and incubating turkey hens were collected and the mid-sagittal sections were dual labeled for either PRL and GH or PRL mRNA and GH. The plasma PRL concentrations were higher in incubating hens (231 +/- 10.6 ng/ml) compared to laying hens (43 +/- 7.4 ng/ml; P<.01). Mammosomatotrophs were predominantly found scattered in the caudal lobe of the anterior pituitary gland, in the ventral half of the cephalic lobe, and dat the junction of the cephalic and caudal lobes. In incubating hens, mammosomatotrophs were found to make up 7.4 +/- 1.52% of the total number of GI-ir and/or PRL-ir cells counted, which was significantly higher (P<.05) than that found in laying hens (0.6 +/- 0.23%). Furthermore, PRL gene expression was also observed in many GH-ir pituitary cells in the incubating hen. These data suggest that (i) mammosomatotrophs are present in the turkey pituitary gland, and (ii) there is an increased abundance of mammosomatotrophs in the incubating turkey hen that may contribute to hyperprolactinemia.