Recovery of secretin in acid small intestinal lumen perfusates in the rabbit

Immunoreactive secretin concentrations were measured in femoral venous plasma and in intestinal perfusates during acid and neutral perfusion of small intestinal segments in anesthetized rabbits. Steady-state plasma and luminal secretin concentrations were less than 20 pg/ml. Duodenal perfusion with with 0.1 N hydrochloric acid stimulated peak plasma immunoreactive secretin concentrations of 200 - 300 pg/ml within five minutes. Acid stimulated plasma concentrations remained constant during 30 minutes of perfusion. Secretin output into the acid perfusate (2000 - 4000 pg/min) accompanied the release into plasma. Subsequent perfusion with a neutral solution resulted in a rapid return to steady-state plasma and luminal secretin concentrations. Sequential acid perfusion of the ileum, jejunum, and duodenum stimulated similar concentrations of secretin in plasma and luminal perfusates.

The pharmacodynamics of bucainide (RHC G233): pharmacokinetic parameters and relationship between plasma levels and the effect on the electrocardiogram in the dog

The pharmacodynamic profile of bucainide dimaleate (RHC G-233) in dogs has been studied. The first observed pharmacologic effect was a change in the ECG pattern (T-wave duration and amplitude) that occurred after an average intravenous dose of 2.7 mg/kg. The average plasma concentration of bucainide was approximately 350 ng/ml. Analysis of data from dogs that received a dual infusion of bucainide indicated that bucainide has an extensive volume of distribution, with an average value of approximately 26 l/kg. An average terminal half-life of 89 minutes was observed. Studies with the radiolabeled drug in rats and dogs also demonstrated the drug's large volume of distribution, and its initial rapid disappearance from the blood. Tissue distribution studies in the rat after administration of the radiolabeled drug showed that bucainide is rapidly taken up by the tissues.

GLC determination of urinary chlorthalidone levels

A sensitive and specific GLC method for the determination of urinary chlorthalidone levels was developed using on-column methylation. Chlorthalidone is converted to a tetramethylated derivative with trimethylanilinium hydroxide in methanol. This method which permits the determination of as little as 0.1 microgram of chlorthalidone/ml of dog urine, should be adequate for use with human subjects receiving a clinical dose.

Chlorthalidone analysis using carbonic anhydrase inhibition

Chlorthalidone was analyzed in the concentration range of 0.1-3.0 microgram/ml with a precision of +/- 0.05 microgram/ml. Chlorthalidone inhibition of the enzymatic hydrolysis rate of p-nitrophenyl acetate by bovine erythrocyte carbonic anhydrase was used as a basis for the determination. The amount of p-nitrophenol formed was measured by monitoring the absorbance at 400 nm, and its formation rate was proportional to the chlorthalidone concentration. The mixing of the enzyme, substrate, and sample, the incubation of the reaction mixture, and the recording of the absorbance were automated. A survey of urine samples from 26 normal human subjects did not reveal any endogenous substances that interfered with the assay. Analyses of urine samples from six subjects after oral administration of 100 mg of chlorthalidone indicated rapid absorption and a biphasic elimination. The alpha-phase half-life was 1.5 hr, and the beta-phase half-life was 35 hr.

GLC determination of nylidrin in human urine samples

A method for the detection of nanogram quantities of nylidrin in human urine is described. The method involves beta-glucuronidase hydrolysis, extraction with chloroform, derivatization by silylation, and GLC determination. The suitability of the method was tested by analysis of urine samples of subjects after oral ingestion of nylidrin hydrochloride.