A B S T R A C T The in vivo hepatic metabolism of connecting peptide (C-peptide) in relation to that of insulin has not been adequately characterized. A radioimmunoassay for dog C-peptide was therefore developed and its metabolism studied in conscious mongrel dogs, with sampling catheters chronically implanted in their portal and hepatic veins and femoral artery. The hepatic extraction of endogenous C-peptide under basal conditions was negligible (4.3±4.5%) and was similar to the hepatic extraction of C-peptide measured during the constant exogenous infusion of C-peptide isolated from dog pancreas. Simultaneously measured hepatic extraction of endogenous and exogenously infused insulin were 43.8±7.6 and 47.5±4.4%, respectively. The metabolic clearance rate of infused C-peptide was 11.5±0.8 ml/kg per min and was constant over the concentration range usually encountered under physiological conditions. In additional experiments, the effect of parenteral glucose administration on the hepatic extraction of C-peptide and insulin was investigated. The hepatic extraction of C-peptide (6.2±4.0%) was again negligible in comparison with that of insulin (46.7±3.4%). Parenteral glucose administration did not affect the hepatic extraction of either peptide irrespective of whether it was infused peripherally, intraportally, or together with an intraportal infusion of gastrointestinal inhibitory polypeptide. The fasting C-peptide insulin molar ratio in both the portal vein (1.2±0.1) and femoral

The salivary anticoagulant of the blood-sucking bug Rhodnius prolixus was purified to homogeneity using a protocol consisting of weak cation-exchange, DEAE, hydrophobic-interaction and octadecyl reverse-phase chromatography, yielding a protein with the same N-terminal sequence as nitrophorin 2, one of the four NO haem protein carriers present in the salivary glands of Rhodnius with a molecular mass of 19689 Da [D. Champagne, R.H. Nussenzveig and J.M.C. Ribeiro, (1995) J. Biol. Chem. 270, in the press]. To exclude the possibility of the nitrophorin being a contaminant, another chromatographic protocol was performed, consisting of chromatofocusing followed by strong-cation-exchange chromatography. Again the anticoagulant was eluted with nitrophorin 2. Nitrophorin 2 inhibits coagulation Factor VIII-mediated activation of Factor X and accounts for all the anti-clotting activity observed in Rhodnius salivary glands.

Salivary gland homogenates from 4 genera of triatomine bugs were assayed for anticlotting, apyrase, and vasodilatory activities, and these activities were correlated with the efficiency of each bug species to initiate a blood meal. Antihemostatic activities spanned a large range of values. Apyrase activity in members of the genus Rhodnius was markedly different from that in other genera with respect to their sensitivity to divalent cation activators. Apyrase and vasodilatory activities, but not anticlotting activity, correlated with feeding efficiency of bugs taking a blood meal on a rat. Results are discussed within the context of the evolution of blood-feeding by insects.

A method for the determination of serum lipase, using a one-hour hydrolysis period, is described. Studies of patients with acute pancreatitis have shown significant elevations of the serum lipase consistent with the clinical condition. Simultaneously performed analyses upon sera of patients for lipase and amylase have shown a close parallelism in the values obtained except in salivary gland disease in which there was elevation of serum amylase without increase in serum lipase. Studies designed to characterize the olive oil-splitting enzyme of serum have suggested that this enzyme is lipoprotein lipase.