Studies on the Relationship Between Flow Resistance, Capillary Filtration Coefficient and Regional Blood Volume in the Intestine of the Cat

Abstract F olkow , B., O. L undgren and I. W allentin . Studies on the relationship between flow resistance, capillary filtration coefficient and regional blood volume in the intestine of the cat . Acta physiol. scand. 1963. 57 . 270—283. — The relation between flow resistance, regional blood volume and capillary filtration coefficient (CFC) in the cat's intestine has been quantitatively studied at different levels of vascular smooth muscle activity, and compared to the vascular bed of the skeletal muscles. The resistance vessels of booth these vascular circuits maintain a considerable ‘basal tone’, but the intestine is far richer vascularized, which is obvious from the figures given for flow resistance, regional blood volume and CFC at comparable levels of vascular tone, including maximal vasodilatation. Intestinal CFC is both in absolute and relative terms higher than in the skeletal muscles, as reflected by a definitely larger CFC/blood flow ratio over the entire range of vascular tone. CFC thus increases considerably when vascular tone is reduced and reaches very high figures at maximal vasodilatation. This is thought to reflect an opening up of additional capillaries due to relaxation of their ‘precapillary sphincters’. Reasons arc given for the belief that the glandular mucosal portion is far better vascularized than the smooth muscle portion of the intestine and at maximal vasodilatation CFC of the mucosal portion may be of the order of 1 ml/min Hg/mm/100 g of tissue. Such a figure is in fact comparable to the renal glomerular filtration, when expressed in the same way.