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

Abstract

FOLKOW, B., 0. LUNDGREN and I. WALLENTIN. Studies on the relationship between Jow resistance, capillary jiltration coefjicient 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 a t 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 tonc. 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 wav.For several years the different 'parallel-coupled' circuits of the systemic vascular bed have been studied from a quantitative point of view in this laboratory. Obviously these circuits a r c designed to suit the need of their particular tissues a n d c a n for such reasons b e expected to show considerable differences 2 70

Effects of adrenaline, isoprenaline and histamine on transsinusoidal fluid filtration in the cat liver

“…Factors which influence or control these variables have been reviewed by Mellander & Johansson (1968). Close arterial infusions of isoprenaline cause vasodilatation and increase capillary filtration coefficient in skeletal muscle and intestine in cats (Johnsson & Oberg, 1968; Diana, 1970;Folkow, Lundgren & Wallentin, 1963). The inhibition of precapillary sphincter activity results in an increased capillary surface area due to opening of previously closed capillaries., Histamine causes vasodilatation and an increased capillary permeability which result in fluid filtration from the capillaries (Kjellmer & Odelram, 1965;Appelgren, Jacobsson & Kjellmer, 1966;Dietzel, Massion & Hinshaw, 1969).…”

The Actions of Natural Secretin on the Small Intestinal Vasculature of the Anaesthetized Cat

“…The preparations used were similar to those described previously for the measurement of blood flow, changes in tissue volume and capillary filtration coefficient (CFC) in the small intestine (Folkow et al, 1963;Richardson, 1974 (Richardson, 1974).…”

“…It has previously been demonstrated that changes in CFC may be evoked by vasoactive substances 9 adminstered in doses inadequate to affect the recorded intravascular pressures or the total blood flow through a tissue (Folkow et al, 1963;Richardson, 1974Richardson, , 1975aRichardson, , 1975b.…”

“…Plethysmographic preparations of the cat small intestine have been used previously for the simultaneous measurement of blood flow, changes in vascular capacitance and capillary filtration coefficient (CFC) by Folkow, Lundgren & Wallentin (1963), and these techniques have been evaluated by Mellander & Johansson (1968) and Folkow & Mellander (1970). It has previously been demonstrated that changes in CFC may be evoked by vasoactive substances 9 adminstered in doses inadequate to affect the recorded intravascular pressures or the total blood flow through a tissue (Folkow et al, 1963;Richardson, 1974Richardson, , 1975aRichardson, , 1975b.…”

Communications

“…and total peripheral resistance (T.P.R. (Folkow, Lewis, Lundgren, Mellander & Wallentin, 1964 Cunningham, Lloyd & Patrick (1963) found that in the absence of prevailing hypoxia, noradrenaline has no effect on the sensitivity to CO2. The report of Mustchin, Gribbin, Tattersfield & George (1976) that the fl-blocking drug propranolol impaired the response to CO2 inhalation in hyperoxia was, therefore, unexpected.…”