Comparison of in vitro and in vivo effects of prazosin on lipid metabolism.

The results of an in vitro study indicate that only nonselective and alpha 2-blocking agents are capable of increasing adrenergic-stimulated lipolysis in human adipose tissue. Concentrations in vivo of total triglycerides, total cholesterol, and low-density lipoprotein and very low-density lipoprotein cholesterol did not change with prazosin treatment. It is suggested that the low affinity of prazosin for the cyclase-coupled alpha 2 receptors in human adipose tissue explains the lack of effect of prazosin on lipid mobilization from tissue to blood and the absence of a change in low-density lipoprotein and very low-density lipoprotein cholesterol in vivo. However, there was a significant increase in high-density lipoprotein cholesterol. The prazosin-related increase in the cholesterol ratio in vivo has been interpreted as a beneficial modification of this risk factor, but is not explained by our in vitro observations.