We have recently shown that the octapeptide angiotensin II is a potent stimulus of protein synthesis and growth in cultured cardiomyocytes. The present study was performed to determine if the renin-angiotensin system was involved in regulating cardiac cell growth in vivo. The pressure-overload cardiac hypertrophy model that develops in abdominal aorta-constricted rats was studied. At 7 and 15 days after abdominal aorta constriction, rats developed significant left ventricular hypertrophy. The increase in left ventricular mass was completely prevented in animals fed the angiotensin-converting enzyme inhibitor, enalapril maleate (0.2 mg/ml) in their drinking water. Cardiac afterload was the same in both groups of animals in that carotid artery pressures were not different in conscious awake aortic-constricted animals receiving and not receiving enalapril. These data suggest a direct growth effect of angiotensin II on the left ventricle and indicate a role for the renin-angiotensin system in the cardiac hypertrophy that develops in response to pressure overload. The presence and chamber localization of angiotensinogen mRNA was determined using Northern hybridization and S1 nuclease mapping analysis. Angiotensinogen mRNA, as determined by dot-blot hybridization analysis, was significantly increased in hypertrophied left ventricles at both 7 and 15 days after the surgery, when compared with sham-operated controls. The activity of the circulating renin-angiotensin system, as indexed by plasma renin activity was increased at 1 day following surgery [6.0 +/- 2.0 ng.ml-1.h-1 angiotensin I (control) vs. 41.8 +/- 10.9 ng.ml-1.h-1 angiotensin I (experimental)], but returned to control values by day 3 postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

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The lymphatic absorption of a structured triacylglycerol vs an equivalent physical mixture of the constituent medium-chain triacylglycerol and fish oils was studied. Each of four canines served as its own control in a crossover feeding design with the investigators unaware of diet contents. Lymphatic absorption of n-3 and medium-chain fatty acids peaked within 4-8 h of feeding either diet. The lymph contained more 10:0 fatty acids than 8:0 despite an overall ratio of 10:0 to 8:0 of 0.3 for the diets. The mass of medium-chain fatty acids absorbed in the lymph at measured time points was 2.6 +/- 0.5-fold higher (mean +/- SE of 12 determinations) for the structured triacylglycerol compared with the physical mix. Molecular species analyses revealed that the medium-chain fatty acids in lymph were present as mixed triacylglycerols. The unique molecular structure of these mixed triacylglycerols and the fatty acids at the 2-position may account for the improved absorption.