Vasopressin and oxytocin mRNA regulation in the rat assessed by hybridization with synthetic oligonucleotides.

Vasopressin and oxytocin are nonapeptide hormones that regulate water metabolism and lactation, respectively. To study the regulation of the vasopressin and oxytocin genes at the mRNA level, we constructed a series of synthetic oligonucleotides, from 8 to 15 bases in length, for use in filter-blot hybridization assays (Northern blots) of hypothalamic mRNA levels and for primed synthesis of cDNAs from which we determined the nucleotide sequences of the 5' regions of the vasopressin and oxytocin mRNAs. A 20-fold increase occurred in the amounts of the two mRNAs present in the hypothalami of rats drinking 2% saline for three weeks. In addition, the sequence analyses of the cDNAs provided the complete amino acid sequences of the NH2-terminal signal peptides of the rat vasopressin and oxytocin precursors. Thus, synthetic oligonucleotides consisting of as few as eight nucleotides can be used to prime reverse transcription of specific cDNAs from hypothalamic RNA, and pentadecanucleotide hybridization probes readily detect changes in levels of vasopressin and oxytocin mRNAs in response to osmotic stress.