Role of Prostaglandins in Nitric Oxide-Induced Glial Cell-Mediated Vasodilation in Rat Retina.

We previously identified that NO derived from neuronal cells acts on glial cells and causes vasodilation in the healthy rat retina via the release of epoxyeicosatrienoic acids (EETs) and prostaglandins (PGs) by activation of the arachidonic acid cascade. However, it is not clear which PG types are involved in these responses. The aim of the present study was to identify prostanoid receptors involved in glial cell-derived vasodilation induced by NO in rat retina. Male Wistar rats were used to examine the effects of intravitreal pretreatment with indomethacin, a cyclooxygenase inhibitor; PF-04418948, a prostanoid EP2 receptor antagonist; and CAY10441, a prostanoid IP receptor antagonist, on the changes in the retinal arteriolar diameter induced by intravitreal administration of NOR3, an NO donor. Retinal arteriolar diameters were measured using ocular fundus images captured with a high-resolution digital camera in vivo. The increase in the retinal arteriolar diameter induced by intravitreal injection of NOR3 was significantly suppressed by intravitreal pretreatment with indomethacin and PF-04418948, but not by CAY10441. The dose of PF-04418948 and CAY10441 injected intravitreally in the present study significantly reduced the increase in the retinal arteriolar diameter induced by prostaglandin E2 (PGE2) and prostaglandin I2 (PGI2), respectively. These results suggest that activation of the arachidonic acid cascade and subsequent stimulation of prostanoid EP2 receptors are involved in rat retinal vasodilatory responses evoked by NO-induced glial cell stimulation. Therefore, glial cell-derived PGE2, similar to EETs, may play an important role in retinal vasodilatory mechanisms.

Captopril enhances cardiac vagal but not sympathetic neurotransmission in pithed rats.

The effect of captopril on neurally evoked bradycardia and tachycardia was investigated in pithed rats. Captopril enhanced the vagal nerve stimulation-evoked bradycardia. Angiotensin I reduced the vagal bradycardia, which was reversed by subsequent administration of captopril. Bradykinin did not affect the neurally evoked bradycardia. Captopril and angiotensin I affected neither the exogenous acetylcholine-evoked bradycardia nor the sympathetic nerve stimulation-evoked tachycardia. These results suggest that the interruption of angiotensin II formation by captopril causes less presynaptic inhibition of acetylcholine release via angiotensin II receptors without affecting cardiac sympathetic neurotransmission.

Simple method of methylation for gas chromatographic analysis of S-benzyl-N-acetylcysteine, a metabolite of toluene, in human urine.

A simplified method of methylation for the determination of urinary S-benzyl-N-acetylcysteine (benzylmercapturic acid, SBAC), a metabolite of toluene, by gas chromatography (GC) was developed. Acidified urine samples (pH 2) were extracted once with ethyl acetate and then derivatized to methyl ester (ME) using HCl-methanol. The optimum conditions for derivatization for SBAC and the internal standard (S-phenethyl-N-acetylcysteine) were reaction at 60 degrees C for 20 min. The SBAC-ME was measured by capillary GC. The calibration curve showed good linearity over the range of 0.2 to 5.0 mg/L (r = 0.986). This method was compared with a previously developed diazomethane methylation method for testing urine from subjects who had sniffed toluene. The values obtained by the two different methods were in good accordance. These results suggest that this technique for the methylation of SBAC by means of HCI-methanol is simpler and time-saving, thus making it feasible to determine SBAC and other mercapturic acids in urinary samples obtained from subjects who have been exposed to organic solvents.

Simultaneous analyses of hypoglycemic agents and C-peptide are essential in a homicide case with the combined dosing insulin and insulin-releasing drug.

A 5-year-old girl was given a sulfonylurea hypoglycemic agent, 25 mg of glibenclamide (ten tablets of Euglucon) with two benzodiazepine drugs, 2 mg of estazoram and 0.75 mg of triazolam (one tablet of Eurodin and three tablets of Halcion), by her 37-year-old pharmacist father and then injected with 70 units of insulin (NovoLet 40R). She died several hours after the injection of insulin. Autopsy was carried out 12 h after the death. A glibenclamide level of 103 ng/ml was detected in the serum collected from the heart at autopsy. The serum insulin and C-peptide concentrations were 295 microU/ml and 0.5 ng/ml, respectively. The high level of insulin and the low level of C-peptide indicated that most of the serum insulin was exogenous. The determination of the serum C-peptide concentration was useful to the diagnosis of hypoglycemia caused by exogenous insulin even in the case of co-administration with an endogenous-insulin-releasing agent.