CHANGES IN PITUITARY SOMATOTROPH AND LACTOTROPH DISTRIBUTION IN LAYING AND INCUBATING TURKEY HENS

Turkey hens can rapidly shift from a laying condition to one character ized by ovarian regression, incubation behavior, and hyperprolactinemi a. Although remarkable changes occur in hormonal profiles as turkey he ns pass from a laying to an incubating state, studies have not been un dertaken to examine histochemical alterations of functionally relevant pituicytes in the adenohypophysis. The objective of this study was to compare the immunocytochemical changes in pituitary lactotrophs and s omatotrophs in incubating turkey hens with those of egg laying hens. B ased upon nest visiting and egg production records, laying and incubat ing hens were selected for sampling blood, pituitaries, and ovaries. P lasma prolactin (PRL) and growth hormone (GH) concentrations were dete rmined. Sagittal pituitary sections of laying and incubating hens were immunostained using antibodies against turkey growth hormone or synth etic chicken PRL peptide. Somatotrophs were found predominantly in the caudal lobe while lactotrophs occurred only in the cephalic lobe of a denohypophysis in laying hens. In incubating hens, somatotrophs in the ventral half of the caudal lobe were replaced by lactotrophs. The sag ittal area which immunostained for PRL was significantly greater while the area that immunostained for GH was less in the adenohypophysis of incubating turkey hens. Some of the lactotrophs were hypertrophied in incubating hens. The lactotrophic recruitment and hypertrophy provide a cellular basis for the hyperprolactinemia in incubating turkey hens . (C) 1996 Academic Press, Inc.