title: Insulin's effect on Leucine turnover changes during early fasting in the conscious dog.
abstract: To study the effects of insulin on leucine turnover during fasting, acute insulin deficiency was induced by the simultaneous infusion of somatostatin and glucagon in conscious dogs fasted 18 h (N = 10) and 48 h (N = 11). Insulin levels during the basal period (before hormone perturbation) were similar in both groups of dogs (12 +/- 3 versus 10 +/- 3 microU/ml, respectively). Glucagon levels were similar in the two groups (94 +/- 9 versus 106 +/- 19 pg/ml). Leucine levels rose from 118 +/- 9 mumol/L to 155 +/- 12 mumol/L as fasting progressed (P less than 0.005). Its rate of appearance also increased by 30% (P less than 0.005) from 3.4 +/- 0.3 to 4.3 +/- 0.4 mumol/kg/min (P less than 0.005), while its clearance remained unchanged. Acute insulin deficiency caused an increase in leucine levels in both 18-h and 48-h-fasted dogs by 55% (to 181 +/- 10 mumol/L) and 45% (to 225 +/- 20 mumol/L), respectively (P less than 0.005). However, while the rate of appearance of leucine remained unchanged in dogs fasted overnight, it rose to 5.1 +/- 0.3 mumol/kg/min (P less than 0.01) in those fasted 48 h. The metabolic clearance rate fell in both groups, although this drop was twice as great in the 18-h group (from 28 +/- 3 to 17 +/- 3 ml/kg/min, P less than 0.005) as in the 48-h group (from 28 +/- 3 to 23 +/- 2 ml/kg/min, P less than 0.005). We conclude that insulin has disparate effects on protein turnover as fasting becomes more prolonged.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.forename: B
authors.initials: B
authors.lastname: Hoxworth
authors.forename: B
authors.initials: B
authors.lastname: Miller
authors.forename: P
authors.initials: P
authors.lastname: Radosevich
authors.forename: R
authors.initials: R
authors.lastname: Buckspan
authors.forename: W
authors.initials: W
authors.lastname: Lacy
authors.forename: N N
authors.initials: NN
authors.lastname: Abumrad
mesh_terms: D000818:Animals; D004285:Dogs; D005215:Fasting; D005260:Female; D005934:Glucagon / Q000494:pharmacology; D007328:Insulin / Q000172:deficiency / Q000502:physiology*; D007700:Kinetics; D007930:Leucine / Q000097:blood / Q000378:metabolism*; D008297:Male; D013004:Somatostatin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D007328:Insulin; D013004:Somatostatin; D005934:Glucagon; D007930:Leucine