Indocyanine green (ICG) obeyed the Beer-Lambert law within the concentration range 1.25 micrograms/ml-10.0 micrograms/ml in distilled water, methanol, dimethylformamide (DMF), 1.2-propanediol and aqueous buffers (pH 9.0), but only up to 7.5 micrograms/ml in human bile and 0.5% human albumin, and only to 5.0 micrograms/ml in human duodenal fluid. ICG was rapidly (less than 1 h) decomposed to a colorless derivative at pH less than 5 and greater than 11, but remained relatively stable for 48 h at pH 8-10. ICG is an indicator and a weak acid with a pKa of 3.27. In bile stabilized with 25% methanol, the precision of the method (CV) is 5% and the accuracy is 106-127%.

Extracellular ATP has vasodilatory and inotropic effects in the heart. We have demonstrated that extracellular ATP, in a concentration-dependent manner (1 0 nM -0.1 mM), increased [Ca' 'Ii in suspensions of isolated fura-2-loaded rat cardiac ventricular myocytes (maximum 96 f 10% increase over basal levels, SEM, n = 12, P < 0.01).The increase in [Ca2+Ii was often biphasic, with an initial fast phase ( < 1 s) of low amplitude, followed by a slower phase of higher amplitude. A second application of ATP had little effect, and ATP abolished the effect of subsequent electrical stimulations, even through the cells were still able to respond with an increase in [CaZ+Ii to KCI-

Physicochemical studies were carried out on the tricarbocyanine dye indocyanine green in biological fluids and organic solvents. The molar lineic absorbance of the compound was highest in organic solvents (methanol, 1.2-propanediol, dimethylformamide) and bile, but lowest in water and duodenal fluid. Indocyanine green remained stable in methanol and bile (t 1/2 > l year) but was rapidly decomposed to a colourless derivative in duodenal fluid and distilled water (t 1/2 3.6 days and 1.4 days, respectively). It was thermostable (120 °C) in methanol and 1.2-propanediol but thermolabile in water and dimethylformamide where the activation energy for the decofnposition reaction was low. At ambient temperature (20 °C) indocyanine green was particularly labile at pH < 5 and pH > 11. The rate of decay of indocyanine green in various solvents indicated that the rate limiting Step in the decay process was either a first or zero order reaction.Physikochemische Untersuchungen an Indocyaningrün: Molare lineare Absorbanz, pH-Toleranz, Aktivierungsenergie und Zerfallsgeschwindigkeit in verschiedenen Lösungsmitteln Zusammenfassung: An dem Tricarbocyaninfarbstoff Indocyaningrün wurden physikochemische Untersuchungen in biologischen Flüssigkeiten und organischen Lösungsmitteln durchgeführt. Die molare lineare Absorbanz der Verbindung war am höchsten in organischen Lösungsmitteln (Methanol, 1,2-Propandiol, Dimethylformamid) und Galle, am. geringsten in Wasser und Duodenalsaft. Indocyaningrün war in Methanol und Galle stabil (tj/2 > l Jahr), wurde jedoch in Duodenalsaft und destilliertem Wasser sehr schnell zu einem farblosen Abkömmling zersetzt (ti/ 2 3,6 bzw. 1,4 Tage). Es war thermostabil (120 °C) in Methanol und 1,2-Propandiol, jedoch thefniolabil in Wasser und Dimethylformamid, in denen-die Aktivierungsenergie für die Zersetzungsreaktion niedrig war. Bei Umgebungstemperatur (20 °C) war der Farbstoff besonders labil bei pH<5 und pH> 11. Die Zerfallsgeschwindigkeit von Indocyaningrün in verschiedenen Lösungsmitteln zeigte, daß der Zerfallsprozeß eine Reaktionskinetik erster oder nullter Ordnung folgt.

Gallbladder storage and emptying patterns were studied in fasting normal subjects by a duodenal perfusion technique using indocyanine green as a biliary marker. Fasting gallbladder storage patterns were very variable but a more uniform biliary output with net storage of about 40% of the biliary marker was observed during a simulated interprandial state (2--4 h after meals) produced by a low dose intravenous infusion of secretin and caerulein. With this background hormonal stimulation, infusion of bovine pancreatic polypeptide to achieve physiological interprandial levels promoted further gallbladder storage of bile. Bovine pancreatic polypeptide produced storage by a major effect on the gallbladder rather than on the liver, common bile duct or sphincter of Oddi since a reduction of biliary output was not observed during bovine pancreatic polypeptide infusion in cholecystectomized subjects. Bovine pancreatic polypeptide had a separate effect on the pancreas, reducing trypsin output in both normal and cholecystectomized subjects.

1. A standard duodenal perfusion technique was used to study the effects of luminally perfused sodium taurocholate on basal and stimulated biliary and pancreatic secretion and gastrointestinal hormone release in man. 2. During duodenal perfusion with sodium taurocholate alone, both basal and caerulein/secretin-stimulated bilirubin secretion were suppressed. A successive perfusion with a mixture of the bile salt and essential amino acids in combination overcame the biliary suppression and biliary secretion rose above basal levels. A further increase in bilirubin secretion was not observed in a subsequent perfusion with essential amino acids alone in these studies. 3. No inhibitory effect on basal or caerulein/secretin-stimulated trypsin secretion was observed during the bile salt perfusion; basal trypsin secretion was in fact slightly increased during a prolonged (4 h) perfusion of the bile salt. 4. During bile salt perfusion, basal bicarbonate secretion remained unchanged but caerulein/secretin-stimulated bicarbonate secretion was slightly increased. 5. Plasma levels of pancreatic polypeptide, gastric inhibitory peptide and gastrin did not change significantly during duodenal perfusion with bile salt, but plasma levels of motilin were suppressed. 6. These results support the view that bile salts in the duodenum may regulate biliary and pancreatic secretion in man and affect plasma levels of motilin.