The Depressive Action of Ammonium Chloride on the Hepatic Blood Flow in Sheep

Abstract

Using the 133Xe clearance method it is shown that NH4Cl infusion into the anterior mesenteric vein decreased capillary blood flow in the liver. Phentolamine completely and propranolol partially prevented the depressive action of NH4Cl on hepatic blood flow. NH4Cl infused into the jugular vein provoked a slight increase in the hepatic blood flow. The adrenaline-like action of ammonium ion on the blood circulation in the liver region is discussed.Blood flow in the vessels of the portal system in ruminants has been the topic of only a few reports [reviewed by Webster, 1974] despite the peculiarity of the digestive processes in these animals. Sellers, Stevens and McLeod [1964] and Sellers [1965] showed that the increased concentration of volatile fatty acids as well as CO2 in the rumen fluid caused a con)siderable rise of blood flow iln the rumen wall. The portal blood flow increased proportionally to the amount of metabolizable energy intake in the feed [Webster and White, 1973]. Weekes and Webster [1975] also confirmed the stimulating influence of volatile fatty acids on blood flow through the liver.Since ammonium ion has been recognized as an adrenaline-like agent in the regulation of tissue metabolism [Prior, Cliford, Gibson and Visek, 1971, Wiechetek, Garwacki andBarej, 1975] one could expect its depressive influence on the blood circulation in the liver. However, the influence of dietary protein level on the blood flow in the portal vein could not be assessed [Webster, 1974]. It seems that in normal conditions of digestion the influence of rumen volatile fatty acids dominates the regulation of physiological processes in this region.Therefore in the present paper we attempted to evaluate changes in the blood flow through the liver of sheep loaded with ammonium chloride through the portal vein and jugular vein. Simultaneously the pharmacological blockade of alpha and beta adrenergic receptors has been used for estimation of the adrenaline-like action of ammonia on the hepatic circulation.99

Whole-body fuel selection in ruminants: nutrient supply and utilization by major tissues

“…There has been one report of this effect on blood flow (Ahmed et al 1983). Transient redistribution of cardiac output among body tissues in favour of peripheral tissues, associated with excess NH3 loading (Orzechowski et al 1987;Fernandez et al 1990) could be under adrenergic regulation (Barej et al 1980). In the present case arterial urea-N but not NH3-N concentrations were increased (P<O-05) with increased CP.…”

Hepatic Capacity for Ammonia Removal in Sheep

“…However, when ammonia was infused in an amount resulting most likely in a slight peripheral hyperammonemia there was observed initially a fall, then an increase, in the hepatic blood supply (P < 0.05, Table 2). The increased inflow of ammonia via the portal vein can suggest its locally sympathetic-like vasoconstrictor influence (BAREJ et al, 1980). Alternatively, the inverse situation of a forcible extension of hepatic efficiency to remove ammonia may have provoked a rise in the portal and hepatic blood flow, probably due to the depressive effect of ammonia on the vasomotor centres in the central nervous system (SCHENKER, 1967;WALKER and SCHENKER, 1970).…”