A B S T R A C T Human umbilical arteries are unique vessels in that they close quickly and completely at birth. It

Estensen et al. (7) found that certain agents, e.g., carbamylcholine, which may raise the intracellular concentration of 3',5'-guanosine monophosphate (cyclic GMP), stimulated polymorphonuclear leukocyte (PMN) chemotaxis, while Goetzl et al. (10) showed that ascorbic acid enhanced movement of monocytes and of PMN. In this paper we show that ascorbic acid and carbamylcholine, like serotonin (12), can cause accumulation of cyclic GMP in human monocytes and that all stimulate leukotaxis of these cells. Cholinergic stimulation increases cyclic GMP in several tissues (IlL Serotonin elevates cyclic GMP in the uterus (I I) and human umbilical artery (6) as well as in monocytes, but no effects of ascorbic acid on cyclic GM P in leukocytes have been previously recorded. MATERIALS AND METHODSLeukocyte fractions were prepared by dextran sedimentation (12) (PMN) or Ficoll-Hypaque separation (Ficoll, Pharmacia Fine Chemicals Inc., Piscataway, N. J.) (3) (mononuclear cells) from normal human blood as previ-480

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A B S T R A C T In an attempt to define the relationship between plasma insulin and triglyceride concentrations, we have studied the effect of suppression of the postprandial insulin response upon the secretion and plasma concentration of very low density lipoprotein (VLDL)-triglycerides. Eight nondiabetic subjects with a wide range of fasting plasma triglyceride levels (100-358 mg/dl) were studied during three dietary periods: base line, high carbohydrate (80% calories), and high carbohydrate (80% calories) with a daily intravenous infusion of somatostatin (SRIF) (1.3 ,g/min) between 800 and 2,100 h. The significant increase in postprandial insulin response observed during high carbohydrate vs. base line was completely abolished during high carbohydrate-SRIF. However, plasma triglyceride levels rose in all subjects during each high carbohydrate period (with/without SRIF) vs. base line and the mean values reached during each period were the same (476±165 vs. 482±152 mg/dl, respectively). The secretion of VLDL-triglyceride into plasma was higher in four subjects, the same in two subjects, and lower in one subject during high carbohydrate-SRIF vs. high carbohydrate alone. The mean production rate of VLDL-triglyceride (mg/kg per h) was 25.6±4.9 during the high carbohydrate and 40.9±28.1 during This work was presented in part in abstract form at the

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