Figure 2.

Effect of pertussis toxin on AVP-dependent cyclic AMP accumulation and on the inhibitory effect elicited by either clonidine, A23187 or PGE₂ in the rat OMCD. (A) Absolute values of cyclic AMP accumulation induced by 1 nM AVP in the presence of 50 μM Ro 20-1724 in control and PTX-treated OMCD. Tubule samples were microdissected from the same kidney and preincubated 2 h at 30°C either in the control medium or in the presence of 500 ng ml⁻¹ PTX. Data are the mean values±s.e.mean calculated from three experiments. ^*P<0.005 or 0.001 in individual experiments when compared to the corresponding response obtained with AVP in control tubule samples. (B) In experiments presented in (A), the effect elicited by 1 μM clonidine, 50 nM A23187 or 0.3 μM PGE₂ on AVP-dependent cyclic AMP accumulation was tested in control and PTX-treated OMCD. Data are expressed in percentage of the corresponding response to 1 nM AVP and are given as the mean values±s.e.mean; ^*P<0.005 or 0.001 in individual experiments when compared to the corresponding response to AVP.