Hemodynamic responses to DOCA in young pigs.

Hemodynamic variables were measured in 20 young pigs; thirteen received subcutaneous implantations of desoxycorticosterone acetate (DOCA) impregnated in Silastic strips, seven received implants of Silastic strips alone and served as controls. No salt was added to the standard diet of either group. Mean arterial pressure (MAP) rose in a regular pattern in the DOCA-treated pigs, reaching on the average a level significantly greater than that of the control group 48 hours after the implantation. Pressure continued to rise, reaching a plateau 38% above that of the preimplant value 2 weeks later. In some pigs the MAP elevation was caused by an increase in cardiac output (CO); in others it was caused by an increase in total peripheral resistance (TPR). An increase in central venous pressure occurred in many DOCA-treated pigs regardless of whether the increase in MAP was caused by an increase in CO or in TPR. The results indicate that it is arterial pressure per se that is the regulated variable in this model of mineralocorticoid hypertension. The regulating system, whether it resides in the kidney or in the central nervous system, elevates pressure by effecting increases in either CO or TPR.