Brain tyrosine availability and the depression of central nervous norepinephrine turnover in acute and chronic starvation in adult male rats.
Norepinephrine (NE) and 3-methoxy-4-hydroxyphenylglycol (MOPEG) were determined in medio-basal hypothalamus of adult male rats using high-performance liquid chromatography to study nutritional modulation of noradrenergic turnover. Acute starvation, as well as 3 weeks of semistarvation with a low-protein high-carbohydrate or high-protein low-carbohydrate diet decreased NE turnover significantly, as estimated by MOPEG concentration. Low-protein semistarvation resulted in subnormal concentrations of large neutral amino acids (LNAA), high-protein semistarvation in elevated concentrations. Tyrosine/LNAA ratio and calculated tyrosine flow into brain and brain tyrosine levels were reduced in both types of semistarvation. Corticosterone was low in low-protein and high in high-protein diet. These results suggest that tyrosine availability in brain potentially contributes to reduced NE turnover in starvation.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D007033:Hypothalamus, Middle / Q000378:metabolism; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000032:analysis; D009638:Norepinephrine / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000378:metabolism*; D014443:Tyrosine / Q000032:analysis*
D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D014443:Tyrosine; D008734:Methoxyhydroxyphenylglycol; D009638:Norepinephrine