AVP and dDAVP in rabbit cortical collecting tubule: a comparative time-course study

The V2-selective analogue of arginine vasopressin (AVP), dDAVP, has been used to distinguish between the effects of V1- and V2-receptor activation by AVP in different cell types of the kidney. Based on studies showing different effects of AVP and dDAVP on prostaglandin secretion, and also on cytosolic Ca2+, we designed a comparative time-course study of both agonists on rabbit microdissected cortical collecting tubules (CCT) microperfused in vitro at 38 degrees C. Plots of the effects of AVP (10 microU/ml or 2.2 x 10(-11) M and 100 microU/ml or 2.2 x 10(-10) M) and dDAVP (10 microU/ml or 0.8 x 10(-11) M) on osmotic water permeability (Pf) at comparable antidiuretic activities, revealed an increase of Pf that was maintained for as long as 170 min of hormone exposure. Also the magnitude of increase in Pf and the time required to achieve the more sustained phase of response were comparable, with no significant difference between the two agonists. These results clearly demonstrate a stable response of rabbit CCT to AVP and dDAVP at physiological temperature, and they reveal no evidence for a difference between the native hormone AVP and its V2 selective analogue on the net hydrosmotic response of the CCT.