CHANGES IN POLY(A) TAIL LENGTH OF ARGININE VASOTOCIN MESSENGER-RIBONUCLEIC-ACID IN THE HYPOTHALAMUS OF WATER-DEPRIVED CHICKENS

The effects of water deprivation on the secretion of vasotocin (AVT) a nd expression of the AVT gene were studied in White Leghorn cockerels. Animals deprived of water far 4 days were compared with normally hydr ated controls. Blood samples were obtained for measurements of plasma osmolality and AVT levels, and the hypothalamus was collected for extr action of total cellular RNA. A 519-bp AVT cDNA was prepared by revers e transcriptase-polymerase chain reaction and a 209-bp PstI/EcoRI rest riction fragment from the 3' region of the fowl AVT cDNA was used as a probe for Northern blot analysis. Plasma osmolality and AVT levels in dehydrated birds were about 30 and 350% greater, respectively, than t hose in normally hydrated controls. The quantity of hypothalamic AVT m RNA was 2.3-fold greater in water-deprived birds compared to controls. The size of the hypothalamic AVT transcript was about 100-bp longer i n the water-deprived birds. As determined by RNase H treatment in the presence and absence of oligo(dT)(12-18), the increase in mean size of the AVT mRNA in dehydrated animals was due to a longer poly(A) tract. Our results indicate that osmotic stress up-regulates expression of t he AVT gene and increases the accumulation of AVT mRNA in the hypothal amus. This accumulation may, in part, be due to lengthening of the AVT mRNA poly(A) tail which is a general mechanism associated with stabil ization of vertebrate mRNAs. (C) 1996 Academic Press, Inc.