STRAIN, AGE AND SEX-DIFFERENCES IN THE RELEASE OF VASOPRESSIN FROM THE PITUITARY - A STUDY IN THE SPONTANEOUSLY HYPERTENSIVE (SHR) AND WISTAR-KYOTO (WKY) RAT

The basal and depolarization-induced arginine-vasopressin (AVP) releas e from intact pituitaries of SHR and WKY rats was studied in vitro in a perfusion chamber. Differences associated to strain, sex and two age periods (preadult: 25-30 days of age; adult: 60-70 days of age) were assessed. The results show an enhanced AVP release in the adult male a s well as female SHR compared to the WKY rat. The stimulated AVP relea se was also significantly higher in the preadult male SHR and indicate d in preadult females SHR. No differences associated to strain in basa l AVP release were detected at the age interval 25-30 days. The respon se to muscimol was increased in preadult female and male SHR rats comp ared to the WKY animals. It is concluded that the augmented depolariza tion-induced AVP release and sensitivity to muscimol in the SHR is not related to sex, and no apparent change in this pattern was associated to the transition between the juvenile and adult condition.