Comparative studies of the venous resistance and capacitance functions and their sympathetic regulation in skeletal muscle.
The relation between the capacitance response (regional blood volume mobilization) and the venous resistance response, i.e. the two main functions of the venous system, was investigated during graded sympathetic nerve excitation in cat gastrocnemius muscle under well defined experimental conditions. The neural capacitance response was also compared with the total regional vascular resistance response and its precapillary resistance component. A reliable distinction between precapillary and postcapillary resistance reactions was made possible by a whole-organ technique permitting continuous recordings of hydrostatic capillary pressure. In the control state, in which a transcapillary fluid equilibrium prevailed, total regional vascular resistance response, precapillary resistance component and venous resistance response averaged 16.6, 14.5 and 2.1 PRU, respectively and total regional blood volume was calculated to comprise 1.0 ml 100 g tissue-1. Graded sympathetic activation, causing graded increments in total regional vascular resistance response, precapillary resistance component and venous resistance response by maximum values of 96, 88 and 8 PRU respectively, were associated with graded decrease in total regional blood volume, at maximum by an average value of 0.57 ml 100 g tissue-1. The relations between regional blood volume mobilization on the one hand, and total regional vascular resistance response, precapillary resistance component and venous resistance response on the other, were all non-linear, implying that the sympathetic volume decrease per unit resistance increase was greater for small than large resistance increases.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Physiology and Biophysics, University of Lund, Sweden.
J
J
Björnberg
M
M
Maspers
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001809:Blood Viscosity; D001810:Blood Volume / Q000502:physiology*; D002196:Capillaries / Q000502:physiology; D002415:Cats; D066298:In Vitro Techniques; D009132:Muscles / Q000294:innervation / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*; D014655:Vascular Resistance / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology