PRESENCE AND SYNTHESIS OF VASOTOCIN IN THE PINEAL GLAND OF BRATTLEBORO RATS

The pineal gland of all mammals so far investigated contains arginine-vasotocin (AVT; Pavel & Petrescu, 1966) or lysine-vasotocin (Pavel, 1965), except that of the homozygous Brattleboro rat with hereditary hypothalamic diabetes insipidus, in which apparently no radioimmunoassayable vasotocin could be detected (Rosenbloom & Fisher, 1975). Since it has been demonstrated recently that the pineal glands of normal rat foetuses contain(Pavel, Goldstein & Calb, 1975) and synthesize (Pavel, Goldstein, Ghinea & Calb, 1977) relatively large amounts of AVT, we investigated the possible occurrence and synthesis of AVT in the pineal glands of foetal homozygous Brattleboro rats. We also studied the pineal glands of adult homozygous Brattleboro rats to test for the presence of AVT. The methods of assay used have been described previously (Pavel, 1965) and included rat antidiuretic, rat uterine and frog (Rana temporaria) bladder assays. Synthetic AVT with a potency of 110 ± 18 (s.d.) rat antidiuretic and 18 000 + 2000 (s.d.) hydro-osmotic units/mg(supplied by Professor M. Bodanszky, Cleveland, Ohio) was used as standard. Highly purified crystalline trypsin (chymotrypsin-free, Serva, Heidelberg) was used for tryptic digestion of culture media and non-incubated pineal glands. Pineal glands from homozy¬ gous Brattleboro rat foetuses, aged 17-19 days post coitum and obtained from homozygous parents, were removed immediately after decapitation and minced to provide a crude dissociated cell suspension. The cells from a single gland were suspended in 1 ml Hank's medium supplemented with 10 % calf serum and 2-5 % N16 medium, as described previously(Pavel et al. 1977). The culture media were initially changed 8 days after establishment of the cultures and thereafter media were changed every 5 days. The antidiuretic and hydro-osmotic activities of cell culture media corresponding to five foetal pineal glands from homozygous Brattleboro rats are shown in Table 1. No rat Table 1. Antidiuretic and hydro-osmotic activities of culture media (1 ml is equivalent to one foetal gland) obtained after the incubation, for various times, of pineal cells from foetal Brattleboro rats (means ± s.e.m.; w = 5