This in vitro study examined the ontogeny of arginine vasopressin (AVP) and arginine vasotocin (AVT) compared with norepinephrine (NE)-mediated contraction in rat thoracic aortas. Aortas from three age groups (2-3 days, 6-7 days, and 12 wk) of Sprague-Dawley rats were used. Ring segment resting length was adjusted to optimize tension developed to a dose that produces half-maximal tension of NE in Krebs solution (pH 7.4, 37 degrees C) and gassed with 95% O2-5% CO2. Cumulative dose-response curves were generated for KCl (5-100 mM), NE (10(-10)-10(-5) M), AVP, and AVT (both 10(-10)-10(-6) M) in the presence and absence of a selective V1 vasopressinergic inhibitor, [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine]arginine vasopressin ([d(CH2)5Tyr(Me)]AVP). A progressive increase in sensitivity among all age groups was found for KCl and NE. There was a slight decrease in sensitivity to both AVP and AVT in the 1st wk. Maximum contractile response to NE increased between 2-3 and 6-7 days, whereas no change was observed for KCl, AVP, or AVT. AVP- and AVT-mediated contractions were selectively inhibited by [d(CH2)5Tyr(Me)]-AVP. These results suggest 1) receptor-mediated contractility is present from 2 days of age for NE, AVP, and AVT; 2) sensitivity to KCl and NE increases progressively during postnatal development, whereas sensitivity to AVP and AVT slightly decreases in the 1st wk with no progressive age-related increase by 12 wk; 3) AVP and AVT mediate contraction via a similar V1-like receptor.

ABSTRACT. We examined the ontogeny of relaxation function may vary depending on the site of binding within responses to three categories of calcium channel antagothe calcium channel. (Pediatr Res 29: 278-281, 1991) nists, represented by verapamil, diltiazem, and nifedipine, for both potential-operated (KCI-mediated) and receptorAbbreviations operated channels [norepinephrine (NE)-mediated] in rat thoracic aorta. Aortic rings from 2-to 3-d, 1-wk, and 12-wk-old Sprague Dawley rats were mounted in an organ bath, bathed in Krebs' solution, and connected to a forcedisplacement transducer to measure isometric tension. Endothelium intact vessels at optimal passive force were exposed to a single EDso of isotonic KC1 or NE, equilibrium contraction was measured, then vessels were washed and exposed for 30 min to 1 pM verapamil, 1 pM diltiazem, or 0.1 pM nifedipine, followed by another dose of KC1 or NE.Verapamil and diltiazem demonstrated significant (p c 0.05) age-related increases in effectiveness for blocking KCI-mediated contraction [(% reduction of control contraction f SEM) (Verapamil: 2-3 d, 67.7 f 4.2; 1 wk, 72.5 f 1.8; 12 wk, 89.5 f 1.0. Diltiazem: 2-3 d, 64.6 f 2.9; 1 wk, 73.5 f 3.0; 12 wk, 83.1 f: 1.81. Nifedipine was equally effective at all ages: 2-3 d, 85.6 f 1.3; 1 wk, 90.0 f 1.6; and 12 wk, 91.3 f 1.4. Verapamil and diltiazem also showed significant age-related increases in effectiveness for blocking NE-mediated contraction (Verapamil: 2-3 d, 6.2 f 3.9; 1 wk, 28.0 f 4.8; 12 wk, 44.1 f 6.0. Diltiazem: 2-3 d, 8.0 f 3.1; 1 wk, 20.5 f 3.9; 12 wk, 46.5 f 4.8). Again, nifedipine was equally effective at all ages: 2-3 d, 42.0 f 6.8; 1 wk, 35.8 f 3.9; and 12 wk, 37.5 f 3.2. In summary, for the categories of calcium channel antagonists that interact at the phenylalkylamine (verapamil) and benzothiazepine (diltiazem) binding sites, there were age-related increases in effectiveness for blocking both potentialoperated and receptor-operated channels. However, for nifedipine, which binds to the 1,4-dihydropyridine binding site, no maturational change was observed. These results suggest that the ontogeny of calcium channel antagonists' We have previously (8) demonstrated the ontogeny of the concentration-dependent response in thoracic aortic rings among 2-d-, 1-wk-, and 1 Zwk-old rats for both potential-mediated (KClinduced) and receptor-mediated (NE-induced) contraction. Thus, calcium channel function is present from 2 d of age with perhaps increasing physiologic function during development. However, many aspects of calcium channel function during ontogeny are unknown. We therefore designed the present study to examine one aspect of calcium channel function, viz. the ontogeny of responses to three categories of calcium channel antagonists for KCI-and NE-mediated contraction in rat aorta. The objectives were 3-fold: to determine if there were 1) agerelated differences in response to selective calcium channel antagonists; 2) differential effects among the three categories of calcium channel antagonists; and 3 ) differe...

Both acute stress hyperglycemia and uncontrolled hypoglycemia may serve as indices of disease severity in critically ill patients, yet the mechanisms behind altered glucose control in inflammatory diseases such as acute sepsis is poorly understood. Evidence of the ability of vasopressin to mediate central and peripheral glucose regulation via V1b and V1a receptors has mounted over the years, but the role of vasopressin in glucose homeostasis during sepsis, is unclear. We hypothesized that vasopressin is involved in glycemic control in endotoxin‐induced inflammation seen in sepsis but that this role may be overshadowed by vasopressin's primary role of maintaining blood pressure in the face of septic shock. Thus, we used a piglet model of endotoxin‐induced pulmonary hypertension in the absence of systemic shock to better understand the relationship between vasopressin and glucose homeostasis in a hypoxemia‐induced inflammatory state. The intent was to study effects of vasopressin separate from its role in blood pressure regulation.After hemodynamic equilibration following catheterization of anesthetized Yorkshire cross piglets (8 kg body weight), baseline mean arterial pressure, cardiac output, and blood gasses were assessed, and blood was obtained for measurement of glucose (BG), vasopressin, cortisol, insulin, glucagon, and cytokine profiles. Liver and pancreatic blood flows were assessed via colored microsphere method. E. coli endotoxin (7,500–50,000 units) was administered intravenously to achieve pulmonary hypertension (evidenced by a pulmonary to systemic vascular resistance ratio increase of 120%), which decreased arterial oxygenation to a PaO2 of 78 ± 5 mm Hg without systemic hypotension(ETX, n=16). Piglets were followed for 11 hours after endotoxin administration. Results were compared against control piglets who did not receive endotoxin (CON, n=7). In CON group, all hemodynamics and biomarkers measured remained constant. Endotoxin caused an increase in pro‐inflammatory markers TNFα, IL‐1ra, and IL‐6. Blood glucose levels were elevated at baseline in both CON (189±11 mg/dL) and ETX (199±9 mg/dL), with corresponding elevated vasopressin levels (106 ± 17 pg/ml; and 78 ± 9 pg/ml in CON and ETX, respectively) likely due to piglet susceptibility to anesthesia induction stress. Both BG and vasopressin levels decreased over the duration of the experiment, with no significant changes in cortisol. Liver blood flow tended to decrease and pancreatic blood flow to increase with time in both CON and ETX. Interestingly, insulin increased 6‐fold with endotoxin and then returned toward baseline by 2 hours after endotoxin administration. Glucagon increased after endotoxin and remained elevated over baseline 11 hours later.Stepwise multiple regression analysis was used to determine relationships between BG and vasopressin, cortisol, insulin, glucagon, TNFα, IL‐1ra, and IL‐6, liver and pancreatic blood flows, hemodynamics, and blood oxygenation. BG was most strongly positively associated with circulating vasopressin, liver blood flow and insulin, and negatively correlated with glucagon (r= 0.72, p<0.001). Our results support an important role of vasopressin as a stress hormone regulator of glucose homeostasis both in control conditions and in the response to endotoxin‐induced stress.Support or Funding InformationThis project was funded by the US Army Medical Command. The views expressed in this abstract are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the U.S. Government.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Endotoxin‐induced shock may be treated with ECMO for cardiopulmonary support. Renal function during ECMO may be altered due to partial cardiopulmonary bypass and altered regulation of cardiovascular regulating hormones. In anesthetized pigs (n=8), we compared renal function at baseline, after endotoxic shock with acute renal failure was established (via i.v. injection of E coli endotoxin), and after 2 hours of stabilization on venoarterial ECMO. Endotoxin caused a mean arterial pressure (MAP) 33% decrease (p≤0.05) from 88±3 to 59±3 mm Hg. ECMO could maintain blood flow to prevent any further deterioration of MAP, but did not return MAP (56±4 mm Hg) to baseline. Interestingly, the 59% decrease (p≤0.05) in renal microcirculatory blood flow (as measured by microsphere method) caused by endotoxin, was prevented from dropping further with ECMO. However, the endotoxin‐induced 76% decrease in GFR (p≤0.05) continued to decline with ECMO resulting in deterioration of urine flow towards complete renal shut down. The urine flow decrease was due mainly to a decrease in osmotic clearance. Results are consistent with the drop of endogenous vasopressin (VP) levels seen with ECMO that we previously reported. We and others have demonstrated that exogenous VP at high doses is needed to reverse renal shut down. Results suggest that during ECMO, VP replacement therapy may be necessary to restore renal perfusion pressure to maintain urine flow.

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