Secretion of prolactin and growth hormone by teleost pituitariesin vitro

Summary The osmotic pressure (OP) of the incubation medium directly affects synthesis and release of prolactin byPoecilia andAnguilla pituitariesin vitro.There is an inverse relationship between the OP of the medium and the amount of prolactin released into the medium (Pigs. 1, 2; Tables 1, 3).Release of newly-synthesised prolactin is similarly related to OP of the medium (Pigs. 3,4; Table 3).Histometric data of prolactin cells also suggests that hormone synthesis is reduced in high OP media (Table 2).Release and synthesis of putative growth hormone (GH) byPoecilia pituitaries is not influenced by OP of the medium (Table 4), butAnguilla pituitaries release more GH in low OP media (Table 5).We thank Mr. W. Thomson for technical assistance. One of us, P. M. I., receives financial support from the Yorkshire Cancer Research Campaign and the work was also supported in part by USPHS Grant AMI-3795. B. I. B. is Sorby Research Fellow of the Royal Society, London.