Regulatory role of vasoactive peptides in subcutaneous skin microcirculation of the hamster.

The microcirculatory effects of vasoactive peptides on arteriolar diameter were determined in the dorsal skin-fold preparation of conscious Syrian hamsters and related to arterial blood pressure (MABP). (5 Ile)-angiotensin II (ANG II), (8 Arg)-vasopressin (AVP), vasoactive intestinal polypeptide (VIP), atrial natriuretic factor (ANF), and substance P (SP) were administered intravenously as bolus injections in picomolar concentrations. The diameters of subcutaneous A3 arterioles (15-40 microns) at bifurcation sites were determined via a microscope video system and stored in a digital memory. When spontaneous rhythmic vasoconstrictions and dilations (vasomotion) were present, the diameter oscillations were analyzed by means of the Prony Spectral Line Estimator. ANG II caused sustained arteriolar contraction at increased MABP, but did neither induce nor modulate vasomotion. Both ANF and VIP slightly reduced MABP and had no effect on microcirculatory parameters. SP led to a significant dilation of subcutaneous arterioles in the hamster skin with concomitant drop in MABP, but did not influence arteriolar vasomotion. Physiological concentrations of AVP, as determined in the plasma by radioimmunoassay, caused a marked contraction of the arterioles and evoked a mild pressor response. In addition, AVP induced or greatly enhanced vasomotoric activity. This study therefore provides evidence that endogenous vasoactive peptides play an important role in regulation of skin peripheral resistance by altering arteriolar diameter in a tonic or even dynamic way.