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

The V₂-selective analogue or 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 boty agonists on rabbit microdissected cortical collecting tubules (CCT) microperfused in vitro at 38°C. Plots of the effects of AVP (10 μU/ml or 2.2 x 10^-11 M and 100 μM/ml or 2.2 x 10^-10 M) and dDAVP (10 μU/ml or 0.8 x 10^-11 M and 100 μU/ml or 0.8 x 10^-10 M) on osmotic water permeability (P(f)) at comparable antidiuretic activities, revealed an increase of P(f) that was maintained for as long as 170 min of hormone exposure. Also the magnitude of increase in P(f) and the time required to achieve the more sustained phase of response were comparable, with no significant difference between the two agonists. The 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.