Catecholamine-induced Lipolysis and Its Relation to Oxygen Consumption in the Newborn Piglet

Abstract

ExtractThe relation between changes in oxygen consumption (VO 2 ) (in milliliters per kilogram and minute) and changes in levels of free fatty acids (FFA) and glycerol in plasma, lactate, pyruvate, and glucose levels in blood, and skin and rectal temperatures following norepinephrine or epinephrine infusions has been studied in neonatal piglets who lack brown fat and rapidly increase their body fat content after birth. Fourteen animals, age 17 hr-13 days (Table L4), each received two 25-min infusions of 2.0 /ig/kg-min of norepinephrine (see Fig. 3); nicotinic acid (50 mg/kg) was administered prior to the second infusion. Five animals, age 5 hr-11 days (Table IB), each received two infusions of 0.2-4.0 /ug/kg-min of epinephrine (Fig. 5).The elevated levels of glucose in blood, and FFA and glycerol concentrations in plasma observed following norepinephrine infusions correlated with postnatal age and body weight, suggesting that the magnitude of the norepinephrine-induced lipid mobilization was dependent upon body fat content. There was no definite tendency for VO2 responses to norepinephrine to increase with increasing postnatal age (Table L4). The increases in glycerol levels (Fig. 2) and FFA ( Fig. 1) concentrations occurring after norepinephrine stimulation were suppressible by nicotinic acid.The increases in VO2 occurring after norepinephrine infusion (Table \A) were small (mean of 0.85 and 0.57 ml/kg-min during infusion prior to and following nicotinic acid administration, respectively) and variable and did not appear to be accentuated by previous starvation for 48 hr; they were related neither to elevations of any of the biochemical variables monitored nor to the small increases in skin and rectal temperatures observed. The changes in VO 2 after epinephrine infusions (Table IB) were quantitatively similar to those recorded during norepinephrine infusions and were not correlated to changes in concentrations of glucose, plasma FFA or glycerol (Fig. 5). SpeculationThe findings in the piglet, of small increases in VO 2 after norepinephrine infusion and the lack of a significant lowering of VO 2 response when norepinephrine challenge was preceded by nicotinic acid administration, contrast with those observed in adults of other species studied and preliminary results found in older piglets. It is therefore suggested that the newborn piglet has a relative inability to increase oxidation of norepinephrine-mobilized FFA and that this may improve with increasing postnatal age.

Body Composition and Cold Resistance of the Neonatal Pig from European (Large White) and Chinese (Meishan) Breeds

“…In the present study, both breeds of pig lets responded to cold by a rise in the plasma concentration of adrenaline and noradrena line as previously reported [11,22]. The increase in the level of plasma glucose level that was observed at both 2 and 24 h of age is consistent with earlier observations [8,26]. This presumably results from the effect of catecholamines on the stimulation of liver glycogenolysis [1,32] and/or on the inhibi tion of glucose uptake by the skeletal muscle [7], The higher level of basal plasma level of FFA in Ms piglets reflects the higher content of fat in colostrum of Ms sows.…”

Metabolic Responses Induced in Neonatal Swine by Norepinephrine, Epinephrine, and Isoproterenol

“…This supports, in part, the observations of Curtis and Rogler and Persson et al that intravenous injections (14) or infusions (12) of norepinephrine induce little or no increases in pIasma NEFA of 6 to 30-hr-old swine. Norepinephrine induced appreciable lipolysis in older animals (> 54 hr) in those studies.…”

“…Persson et at?. (12) demonstrated that norepinephrine infusions induced less increase in blood glucose in young (1-2 days old) than in older (5-12 days old) piglets.…”

Metabolic Response to Thyroxine in the Newborn Pig

“…In fact, a low total plasma-protein-binding capacity for T4 with a concomitant high free T4 level occurs in pigs less than 12 h o f age {Slebodzihski, 1965a) and may thus enable a quicker metabolic action of the hormones. The newborn pig has no ana tomically detectable brown adipose tissue {Leblanc and Mount, 1968;Rowlatt et aL, 1971) and is different from the newborn o f some other species as it does not react metabolically to noradrenaline {LeBlanc and Mount, 1968;Persson et al, 1971;Kaciuba-Uscilko and Poczopko, 1973). On the basis o f these findings it has already been postulated that in the pig T4 is the major hormonal factor responsible for the metabolic adaptation to extrauterine life.…”