AJP - Heart and Circulatory Physiology, Vol 243, Issue 3 491-H497, Copyright © 1982 by American Physiological Society
A comparison of capillary hydraulic conductivities in postural and locomotor muscle
P. F. McDonagh and R. W. Gore
In a comparative skeletal muscle study Folkow and Halicka (Microvasc. Res.
1: 1-14, 1968) reported that the capillary filtration coefficient (CFC) of
postural (red) muscle was two times the CFC of locomotor (white) muscle. It
was concluded that the twofold difference in CFC was due solely to a
difference in the perfused capillary surface areas (Sf) of red vs. white
muscle. However, CFC is the product of capillary hydraulic conductivity
(LP) and Sf. Hence their conclusion assumed that the average LP of red
muscle capillaries is exactly equal to the average LP of white muscle
capillaries. The following study was undertaken to test the validity of
this assumption. The microocclusion procedures and analytical model
described by Lee et al. (Circ. Res. 28: 358-370, 1971) and Gore [Am. J.
Physiol. 242 (Heart Circ. Physiol. 11): H268-H287, 1982] were used to
determine LP. Independent measurements of LP were recorded from single
capillaries in red, anterior latissimus dorsi (ALD) and white, posterior
latissimus dorsi (PLD) muscles of chickens anesthetized with L.A. Thesia.
We found that the mean capillary hydraulic conductivity in postural muscle
[(LP)ALD = 0.20 +/- 0.06 (SE) micrometers . s-1 . cmH2O-1 (n = 11)] was
significantly different from the mean capillary hydraulic conductivity in
locomotor muscle [(LP)PLD = 0.061 +/- 0.01 micrometers . s-1 . cmH2O-1 (n =
14)] (P less than 0.05). These results provide direct evidence that
observed differences in red vs. white muscle CFC's may not be due solely to
different perfused capillary surface areas but may also be due to
differences in capillary hydraulic conductivity.
