Characteristics of myocytes isolated from hearts of renovascular hypertensive guinea pigs.

A model of renovascular hypertension has been developed in the guinea pig using the Goldblatt (2-kidney, 1-clip) operation. Systolic and diastolic blood pressures were significantly increased 3 and 7 wk after the operation, but levels fell to control values at 11 wk. The two-dimensional areas of myocytes isolated from the hearts of Goldblatt-operated (GB) animals were larger than those in control cells at 3 wk (cf. 3,397 +/- 87 and 2,208 +/- 125 microns 2, P < 0.01), and the difference was maintained at 7 and 11 wk. No change in cell contraction or relaxation characteristics were seen at either 3 or 7 wk after clipping. Myocytes from the 11-wk GB group showed a significantly reduced contraction amplitude and velocity at 32 degrees C in maximally activating Ca2+ or isoproterenol concentrations (%cell shortening in Ca2+, cf. 6.8 +/- 0.4 and 10.0 +/- 0.9, P < 0.01). Concentrations eliciting 50% of maximal response for Ca2+ or isoproterenol were unchanged, as was the ratio of isoproterenol to Ca2+ effect in the same cell. Increases in time to peak contraction (TTP) and time to 50% relaxation (R50) were observed in 11-wk GB myocytes, but only at room temperature. There was no lengthening of TTP or R50 of the Ca2+ transient, nor was there any change in Ca2+ current density or inactivation kinetics in these myocytes.