Abstract␤ 1 -and ␤ 2 -adrenoceptors in heart muscle cells mediate the catecholamine-induced increase in the force and frequency of cardiac contraction. Recently, in addition, we demonstrated the functional expression of ␤ 3 -adrenoceptors in the human heart. Their stimulation, in marked contrast with that of ␤ 1 -and ␤ 2 -adrenoceptors, induces a decrease in contractility through presently unknown mechanisms. In the present study, we examined the role of a nitric oxide (NO) synthase pathway in mediating the ␤ 3 -adrenoceptor effect on the contractility of human endomyocardial biopsies. The negative inotropic effects of a ␤ 3 -adrenoceptor agonist, BRL 37344, and also of norepinephrine in the presence of ␣ -and

Administration of CHIKV immunoglobulins may constitute a safe and efficacious prevention strategy and treatment for individuals exposed to CHIKV who are at risk of severe infection, such as neonates born to viremic mothers and adults with underlying conditions. These results provide a proof-of-concept for purifying human immunoglobulins from plasma samples from patients in the convalescent phase of an emerging infectious disease for which neither prevention nor treatment is available.

This study was conducted to evaluate whether treatment of normal and diabetic rat hearts with rosiglitazone, a high-affinity ligand of the peroxisome proliferator-activated receptor-␥ (PPAR-␥) used for the treatment of type 2 diabetes, improves postischemic functional recovery. The effects of acute rosiglitazone administration were investigated using working hearts isolated from normal rat or rats diabetic for 4 weeks after streptozotocin (STZ) injection. Hearts were subjected to 30 min of normothermic, zero-flow ischemia followed by 30-min reperfusion. Rosiglitazone (1 mol/l) administered before ischemia had no effect on cardiac function during baseline perfusion, but it significantly improved aortic flow during reperfusion in both normal and diabetic hearts. In a chronic protocol in which rosiglitazone was given by daily gavage (10 mol/kg body wt) immediately after STZ injection, rosiglitazone also prevented postischemic injury and significantly improved functional recovery. Using Western immunoblotting, it was demonstrated that the acute cardioprotective effect of rosiglitazone is associated with an inhibition of Jun NH 2 -terminal kinase phosphorylation in both normal and diabetic rat hearts. Furthermore, rosiglitazone also inhibited activating protein-1 DNAbinding activity. These data, demonstrating that rosiglitazone limits postischemic injury in isolated hearts, suggest an important function for PPAR-␥ in the heart. Diabetes

Our group recently cloned the electrogenic Na+-[Formula: see text]cotransporter (NBC) from salamander kidney and later from mammalian kidney. Here we report cloning an NBC isoform (hhNBC) from a human heart cDNA library. hhNBC is identical to human renal NBC (hkNBC), except for the amino terminus, where the first 85 amino acids in hhNBC replace the first 41 amino acids of hkNBC. About 50% of the amino acid residues in this unique amino terminus are charged, compared with ∼22% for the corresponding 41 residues in hkNBC. Northern blot analysis, with the use of the unique 5′ fragment of hhNBC as a probe, shows strong expression in pancreas and expression in heart and brain, although at much lower levels. In Xenopus oocytes expressing hhNBC, adding 1.5% CO2/10 mM[Formula: see text] hyperpolarizes the membrane and causes a rapid fall in intracellular pH (pHi), followed by a pHi recovery. Subsequent removal of Na+ causes a depolarization and a reduced rate of pHi recovery. Removal of Cl− from the bath does not affect the pHi recovery. The stilbene derivative DIDS (200 μM) greatly reduces the hyperpolarization caused by adding CO2/[Formula: see text]. In oocytes expressing hkNBC, the effects of adding CO2/[Formula: see text]and then removing Na+ were similar to those observed in oocytes expressing hhNBC. We conclude that hhNBC is an electrogenic Na+-[Formula: see text]cotransporter and that hkNBC is also electrogenic.

Our data provide evidence that inhibition of hhNBC, whose role in cardiac pathologies could be amplified by overexpression, represents a novel therapeutic approach for ischemic heart disease.