Change in liver blood flow and blood content in dogs during direct and reflex alteration of hepatic sympathetic nerve activity.

Abstract

SUMMARY A mean decrease of 60% in liver blood volume was recorded by a plethysmographic technique during electrical stimulation of the hepatic nerves in anesthetized, vagotomized dogs. A decrease in pressure in the vascularly isolated carotid sinus to 40 mm Hg, from a mean control of 144 mm Hg, decreased liver blood volume by a mean of 16%; arterial blood pressure increased by a mean of 77 mm Hg. Carotid sini's hypotension was accompanied by respective mean increases of 16% and 1.4% in hepatic arterial and portal venous blood flows, and of 45% and 22% in arterial and portal resistances. Increase in sinus pressure to 240 mm Hg increased liver blood volume by a mean of 20%; arterial blood pressure decreased by 90 mm Hg. Sinus hypertension was accompanied by respective mean decreases of 10% and 1.5% in hepatic arterial and portal venous blood flows, and of 44% and 18% in arterial and portal resistances. Interruption of afferent vagal traffic from cardiopulmonary receptors was maximally effective in decreasing liver blood volume at a carotid sinus pressure of 40 mm Hg and was ineffective at carotid sinus pressures greater than 160 mm Hg. Combined withdrawal of carotid and cardiopulmonary vasomotor inhibition decreased liver blood volume by 42%; of this 37% was due to the cardiopulmonary and 63% to the carotid baroreflex. The study showed the canine liver to function as a blood reservoir by active mobilization of a portion of its blood volume.THE ABILITY of the sympathetic adrenergic system to modify reflexly splanchnic blood flow and blood volume is well documented. "5 Francois-Frank and Hallion 6 used a plethysmographic technique to demonstrate a decrease in liver blood volume in response to direct and reflex stimulation of hepatic sympathetic nerves in the dog. The technique was modified for use in the cat by Griffith and Emery.7 Liver blood volume decreased during pressor reflexes and increased during depressor reflexes; hemorrhage induced a reduction in liver blood volume. The reactions were abolished on cutting the postganglionic fibers of the hepatic plexus. Further evidence for a reflex control of hepatic capacitance vessels was provided by the studies of Heymans et al., 8 who demonstrated a reduction in liver blood volume during bilateral carotid occlusion in the dog. There is thus considerable evidence for a reflex control of hepatic blood volume mediated through alteration in sympathetic adrenergic nerve activity. However, quantitative measurements could not be made in the above studies.Recently, Greenway and Oshiro 9 reported quantitative measurements of the decrease in liver blood volume during direct stimulation of hepatic nerves in the cat and the dog. Maximal responses were obtained at frequencies of about 6 Hz when 50% of the liver blood volume was expelled. The hepatic capacitance therefore was large and, in contrast to the autoregulatory escape that occurred in the hepatic arterial resistance vessels, the contraction of the capacitance vessels was well sustained through the period of stimulation....

Capacitance of the rabbit portal vein and inferior vena cava.

“…Studies in vivo indicate that there is intrinsic vasomotor tone in the portal vein (Johansson & Ljung, 1967) and that carotid sinus baroreceptors and noradrenaline have sizeable effects on portal venous tone (Alexander, 1954 ;Brooksby & Donald, 1971;Auden & Donald, 1975;Carneiro & Donald, 1977;Richardson & Withrington, 1978 …”

“…The portal circulation has an important capacitance function (Brooksby & Donald, 1971;Mitzner & Goldberg, 1975;Carneiro & Donald, 1977;Donald, 1981). Little is known, however, of the capacitance characteristics of the large extra-hepatic vessels such as the portal vein.…”

Systemic vascular effects of acute electrical baroreflex stimulation

“…Modulation of venous capacitance by sympathetic outflow has been demonstrated with studies during electrical stimulation, including splanchnic and hepatic nerves (5,7), changes in carotid artery pressure (31), and pharmacological manipulation of sympathetic activity (23). The control of vascular capacitance by the carotid baroreflex has been well-investigated and demonstrated (30).…”

Vasomotor center controls of the hepatic circulation during blood pressure oscillation in rabbits.

“…It can be concluded that the effects, if any, of an increase in the catecholamine concentration in the blood on the hepatic circulation were physiologically too weak to be detected. CARNEIRO and DONALD (1977) reported that in the case of reflex hypertension caused by exposing the carotid sinus to local hypotension in dogs, HAF and PVF increased to 116 and 101.4% of the control, respectively. In our study, the maximum increase of HAF and PVF were obtained at the later and initial stages of SPEP, respectively.…”

“…TAKEUCHI, N. TERADA, and S. KOYAMA but the HAF shows ambiguous results: decreases (SELKURT and BRECHER, 1956;GALINDO, 1965;MUNDSCHAU et al, 1966) or increases (SANCETTA, 1953;GREENWAY et al, 1967b). Concerning the influence of reflexes on hepatic hemodynamics, occlusion of the carotid arteries in cats causes systemic arterial pressure (SAP) rise with little change in HAF (GREENWAY et al, 1967a), and carotid sinus hypotension in dogs increases the HAF and PVF (CARNEIRO and DONALD, 1977). Studies have been already made on the hemodynamics of the cutaneous, renal, intestinal, and skeletal muscle vascular beds TAKEUCHI and MIYAKAWA, 1980) and of blood mobilization from the renal, hepatic, jejunal, skeletal-muscle, and hind-paw vascular beds during blood pressure oscillation caused by the side pressure exertion procedure (SPEP).…”