Inhibitory action of guanosine 3',5'-monophosphate on thrombin-induced calcium mobilization in human platelets

During thrombin-induced serotonin release from platelets, phosphorylation of myosin light chain was increased. This protein phosphorylation, which is initiated by Ca2+ mobilization, and serotonin release were inhibited progressively by increasing concentrations of sodium nitroprusside, a potent stimulator of platelet guanylate cyclase, or 8-bromo-cyclic GMP. Thrombin-induced increase in cytoplasmic free Ca2+, which was also inhibited by these drugs in a dose-dependent manner. These results provide evidence that an increase in platelet cyclic GMP inhibits thrombin-induced Ca2+ mobilization and prevents platelet activation.

Determination of total captopril in dog plasma by HPLC after prelabelling with ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (SBD-F)

A HPLC method has been developed for the determination of captopril, an angiotensin-converting enzyme (ACE) inhibitor, in dog plasma. The plasma was deproteinized with trichloroacetic acid (TCA) containing N-(3-mercapto-1-oxopropyl)-piperidine-2-carboxylic acid SQ 25,233 as an internal standard, adjusted to pH 9.5 with borate buffer containing tri-n-butyl phosphine (TBP) to reduce the oxidized captopril, and treated with a thiol specific reagent, SBD-F. The fluorescent derivatives of captopril and the internal standard were separated from other interfering peaks on a reversed-phase column and determined by HPLC. The proposed method was simple, selective and sensitive. The total plasma concentration of captopril reached a maximum of 3.04 +/- 0.54 microg/ml (mean +/- S.E.) 60 min after administration of the drug.

Elevation of cytoplasmic free calcium concentration by stable thromboxane A2 analogue in human platelets

9, 11-Epithio-11, 12-methano-thromboxane A2 (STA2), a stable analogue of thromboxane A2, caused a rapid rise in cytoplasmic free Ca2+ concentration ([Ca2+]i) in human platelets as measured with the fluorescent Ca2+ indicator quin2. Concomitantly, this compound induced phosphorylation of myosin light chain which is catalyzed by Ca2+, calmodulin-dependent protein kinase. These reactions were fast enough to trigger serotonin release. 13-Azaprostanoic acid, a receptor level antagonist of thromboxane A2 inhibited STA2-induced elevation of [Ca2+]i, phosphorylation of myosin light chain and serotonin release. These results provide evidence that STA2 interacts with a thromboxane A2 receptor which leads to elevation of [Ca2+]i.

Effect of cyclic AMP on cytoplasmic free calcium in human platelets stimulated by thrombin: direct measurement with quin2

With the fluorescent Ca2+ indicator quin2, we measured directly cytoplasmic free Ca2+ [( Ca2+]i) in washed human platelets stimulated by thrombin and examined the effect of cyclic AMP on [Ca2+]i levels and 14C-serotonin release. Thrombin (0.2 U/ml) evoked a rise in [Ca2+]i from the basal level of about 100 nM to integral of 3 microM which was fast enough to trigger serotonin release. This rise was inhibited in a dose-dependent manner by preincubation with prostaglandin E1 (PGE1) (0.1-10 microM) or dibutyryl cyclic AMP (0.01 -1 mM). Parallel to this, serotonin release was also inhibited by these drugs. When added to platelets after stimulation by thrombin, PGE1 caused the rapid decrease of elevated [Ca2+]i. These results provide direct evidence that [Ca2+]i levels in platelets are regulated by cyclic AMP.

Protein phosphorylation and diglyceride production during serotonin release induced by epinephrine plus ADP in human platelets

Epinephrine (1 microM) plus ADP (5 microM) induced serotonin release from human platelets although neither epinephrine nor ADP alone brought about such a release. During this release reaction, the phosphorylation of 40K-dalton protein was induced to an extent similar to that induced by 0.5 unit/ml thrombin. The amount of diglyceride (DG) produced by epinephrine plus ADP, however, was much smaller than that produced by thrombin. The reaction velocities of these reactions induced by epinephrine plus ADP were slower than those induced by thrombin. Epinephrine or ADP alone hardly produced any DG and induced 40K-dalton protein phosphorylation only slightly. Indomethacin (1 microgram/ml), a cyclooxygenase inhibitor, remarkably inhibited epinephrine plus ADP induced serotonin release, 40K-dalton protein phosphorylation and DG production although this agent had little effect on the same reactions induced by thrombin. These results suggest that prostaglandin endoperoxides or thromboxane A2 may be involved in serotonin release, 40K-dalton protein phosphorylation and DG production induced by epinephrine plus ADP.

Influence of food on the clinical effect of angiotensin I converting enzyme inhibitor (SQ 14,225)

In order to clarify the influence of food on the clinical effect of angiotensin I converting enzyme inhibitor (SQ 14,225, captopril), 25 mg of the drug was administered to patients with hypertension using in a two-way crossover study design. In the first study (study I), each subject received the drug 30 min after breakfast, and changes in blood pressure (BP), blood concentration of captopril (BCC), plasma renin activity (PRA), plasma aldosterone (PA) and plasma angiotensin I converting enzyme activity (ACE-A) were determined for 3 hr. BP was recorded for 6 hr. Four days after study I, the same subjects received the drug 2 hr after breakfast, and each parameter was again determined (study II), similarly to study I. No significant difference in the hypotensive responses to captopril was observed between both studies during 6 hr of observation. Maximum hypotensive effects were found within 90 min of the treatments in study I and study II, and BP returned almost to baseline levels at 6 hr in both studies. Maximum BCC levels were found 60 and 90 min after the drug administration in studies I and II, respectively, and these approximated to half of each maximum level at 180 min. There were no statistically significant differences in the biological half-life (T1/2), maximum concentration (C max), maximum concentration time (T max), and area under the blood concentration curve [AUC]0(3) between both studies. The peak in PRA occurred at 60 and 90 min after the administration of the drug in studies I and II, respectively. In study I, a slightly greater reduction of PA levels was found, but there was no significant difference in the magnitude of the reduction between both studies. The present results indicate that food did not exert any significant influence on the clinical effect of captopril.

Captopril (SQ 14225) clearance during hemodialysis treatment

The clearance of Captopril (SQ 14225) was examined in six hemodialysis patients, using a newly developed method for the determination of Captopril in blood. At 30 minutes after the start of hemodialysis, the clearance of Captopril was 80 +/- 14.2 ml/min, whereas that of creatinine was 123.4 +/- 8.8 ml/min and that of BUN was 144.1 +/- 7.2 ml/min. The blood concentration of Captopril was found to be lower when taken in a postprandial state than in a fasting state.

A new possible regulatory system for protein phosphorylation in human peripheral lymphocytes. I. Characterization of a calcium-activated, phospholipid-dependent protein kinase

A new species of protein kinase (protein kinase C), found in human peripheral lymphocytes, is 20 times more active than adenosine 3',5'-monophosphate-dependent protein kinase (protein kinase A) with histone as phosphate acceptor. This enzyme is normally present as an inactive form in soluble fraction, but attaches to membrane to exhibit full catalytic activity. This activation process is reversible, and absolutely requires Ca++. No other divalent cations can substitute for Ca++. The enzyme is independent of cyclic nucleotides. The active factor associated with membrane is phospholipid. The protein kinase shows a m.w. of 7.7 X 10(4). The pH optimum is 7.5 to 8.5. GTP does not serve as phosphate donor. The enzyme appears to show relatively broad substrate specificity that is distinctly different from that of protein kinase A. Although both protein kinases C and A react with H1 histone, analysis of the N-bromosuccinimide-bisected fragments of this radioactive histone has revealed that protein kinase C greatly favors seryl and threonyl residues of the C-terminal portion, whereas protein kinase A reacts preferentially with seryl residues in the N-terminal portion of this histone. Protein kinase C is protentially multifunctional and may regulate various Ca++-dependent cellular processes. It is noted that protein kinase C may be alternatively activated in an irreversible manner by limited proteolysis with Ca++-dependent neutral protease. The enzyme activated in this way is independent of Ca++ and membrane.

A new possible regulatory system for protein phosphorylation in human peripheral lymphocytes. I. Characterization of a calcium-activated, phospholipid-dependent protein kinase

A new species of protein kinase (protein kinase C), found in human peripheral lymphocytes, is 20 times more active than adenosine 3',5'-monophosphate-dependent protein kinase (protein kinase A) with histone as phosphate acceptor. This enzyme is normally present as an inactive form in soluble fraction, but attaches to membrane to exhibit full catalytic activity. This activation process is reversible, and absolutely requires Ca++. No other divalent cations can substitute for Ca++. The enzyme is independent of cyclic nucleotides. The active factor associated with membrane is phospholipid. The protein kinase shows a m.w. of 7.7 X 10(4). The pH optimum is 7.5 to 8.5. GTP does not serve as phosphate donor. The enzyme appears to show relatively broad substrate specificity that is distinctly different from that of protein kinase A. Although both protein kinases C and A react with H1 histone, analysis of the N-bromosuccinimide-bisected fragments of this radioactive histone has revealed that protein kinase C greatly favors seryl and threonyl residues of the C-terminal portion, whereas protein kinase A reacts preferentially with seryl residues in the N-terminal portion of this histone. Protein kinase C is protentially multifunctional and may regulate various Ca++-dependent cellular processes. It is noted that protein kinase C may be alternatively activated in an irreversible manner by limited proteolysis with Ca++-dependent neutral protease. The enzyme activated in this way is independent of Ca++ and membrane.

Relationship between blood pressure and blood levels of angiotensin I converting enzyme inhibitor (SQ 14,225)

The time courses of mean blood pressure (MBP), plasma renin activity (PRA), plasma aldosterone (PA), serum prostaglandin E (PGE), serum angiotensin I converting enzyme (ACE), and blood levels of angiotensin I converting enzyme inhibitor (SQ 14,225) (captopril) were studied in 6 patients with essential hypertension (5 men and 1 woman, aged 44 +/- 5.6 (mean +/- S.E.) years) before and 30, 60, 120 and 180 min after administration of 25 mg captopril. MBP and ACE began to fall within 30 min and reached a significant minimum between 60 and 180 min after captopril administration. PRA was significantly increased 60 min after captopril administration and continued for 180 min. On the other hand, PA had begun to fall significantly 180 min after captopril administration. The blood levels of captopril were significantly increased 30 min after captopril administration, with a peak at 120 min. The levels at 180 min were half the peak. The levels of PGE were not significantly changed within 180 min after captopril administration. These results suggest a discrepancy between the changes in MBP and the blood levels of captopril. The blood pressure lowering effect may be due to inhibition of angiotensin II (Ang. II) during the short-acting effect, and due to decrease of PA, metabolites of captopril, increase of kinin in the blood, inhibition of the slow pressor effect of Ang. II, increases of other depressor hormones such as prostacyclin and other depressor mechanisms during the long-acting effect.

Dosage form design for improvement of bioavailability of levodopa IV: Possible causes of low bioavailability of oral levodopa in dogs

Several potential mechanisms for reduced levodopa bioavailability following oral administration to dogs and humans were investigated by studying the influence of the administration route on plasma levodopa levels after intravenous, hepatoportal, and duodenal administrations to dogs. The observed average areas under the plasma concentration-time curves (AUC) of levodopa following hepatoportal injection and intravenous injection were virtually identical; but following duodenal administration a decrease in the AUC of levodopa was observed with a concomitant increase in the AUC of total dopamine. The possible involvement of intestinal microorganisms in levodopa metabolism was explored in dogs that had been administered a combination of paromomycin and kanamycin to reduce intestinal microflora. Similar patterns of plasma level profiles and urinary excretion were observed between control and treated dogs. As measured by the release of [14C]carbon dioxide from [14C]levodopa, the distribution of levodopa decarboxylase enzyme activity in various parts of the intestine was studied in homogenates prepared from isolated intestinal segments of the duodenum and upper, middle, and lower parts of the jejunum and ileum. The jejunum showed the highest decarboxylase activity followed by the ileum and duodenum. These data indicate that the reduced bioavailability of orally administered levodopa occurs as a result of metabolism by levodopa decarboxylase enzyme in the gut wall.

Blood concentration and urinary excretion of captopril (SQ 14,225) in patients with chronic renal failure

Blood concentration and urinary excretion of captopril following 50 mg oral administration were determined by high-performance liquid chromatography in normal subjects and patients with chronic renal failure. In normal subjects, the maximum blood concentration of the free form of captopril was obtained within 1 hour and was not detectable after 6 hours; 41% of administered captopril was excreted into the urine as free form and metabolites within 2 hours, and 58% within 6 hours. In chronic renal failure patients with an average serum creatinine of 5.1 mg/dl, the absorption constant (Ka), maximum concentration (Cmax), and area under the blood concentration curve (AUC) were not significantly different from those in the normal subjects, but the elimination constant (Ke) and biological half-life (T1/2) showed a significant delay in the disappearance of captopril from the blood (p less than 0.01 respectively). The cumulative amount of urinary excretion of either free-form captopril or its' metabolites was significantly decreased at 2, 4, and 6 hours in chronic renal failure patients (p less than 0.01 or less, respectively). Impairment of kidney function is suggested to be an important factor in the promotion of blood retention of captopril.

Possible involvement of Ca2+-activated, phospholipid-dependent protein kinase in platelet activation

Ca2+-activated, phospholipid-dependent protein kinase recently found in rat brain (Takai, Y., Kishimoto, A., Iwasa, Y., Kawahara, Y., Mori, T., & Nishizuka, Y. (1979) J. Biol. Chem. 254, 3692-3695) is present in large quantities in human platelets. The activation of this enzyme appears to be initiated by unsaturated diacylglycerol and intimately related to phosphatidylinositol hydrolysis which is induced by thrombin. The enzyme is selectively and profoundly inhibited by several phospholipid-interacting compounds such as imipramine, verapamil, and tetracaine, which concomitantly inhibit aggregation and release reaction in parallel manners. It is suggestive that this protein kinase may be involved in the transmembrane control of intracellular events eventually leading to platelet activation.

A role of membranes in the activation of a new multifunctional protein kinase system

A new multifunctional protein kinase, which normally exists as an inactive form in the soluble fraction in mammalian tissues, attaches to membranes to exhibit full enzymatic activity. A low concentration of Ca2+ is absolutely necessary for this activation. This process is reversible. cAMP shows no effect. The active factors in membranes are phosphatidylinositol, phosphatidylserine, phosphatidic acid, diphosphatidylglycerol, and phosphatidylethanolamine in that order. Phosphatidylcholine and sphingomyelin are far less effective. Cytoplasmic as well as other membrane fractions from various tissues are active in supporting the enzymatic activity. A possible role of this Ca2+ and phospholipid-activated protein kinase system in transmembrane control is proposed.

Calcium-dependent activation of a multifunctional protein kinase by membrane phospholipids

The proenzyme of a Ca2+-dependent protease-activated protein kinase previously obtained from mammalian tissues (Inoue, M., Kishimoto, A., Takai, Y., and Nishizuka, Y. (1977) J. Biol. Chem. 252, 7610-7616) was enzymatically fully active without limited proteolysis when Ca2+ and a membrane-associated factor were simultaneously present in the reaction mixture. The activation process was reversed by removing Ca2+ with ethylene glycol bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid. An apparent Ka value for Ca2+ was less than 5 x 10(-5) M. Other divalent cations were inactive except for Sr2+, which was 5% as active as Ca2+. The factor was almost exclusively localized in membrane fractions of various tissues including brain, liver, kidney, skeletal muscle, blood cells, and adipose tissue. It was easily extractable with chloroform/methanol (2:1), and was recovered in the phospholipid fraction. In fact, this membrane factor could be replaced by chromatographically pure phosphatidylinositol, phosphatidylserine, phosphatidic acid, or diphosphatidylglycerol. Phosphatidylethanolamine, phosphatidylcholine, and sphingomyelin were far less effective under the comparable conditions. Ca2+-dependent modulator protein was unable to support enzymatic activity. The enzyme thus activated showed an ability to phosphorylate five histone fractions and muscle phosphorylase kinase, and appeared to possess multifunctional catalytic activities.

Clinicopathological study of soft tissue tumors

Clinical aspects of patients with soft tissue tumors encountered at the Department of Orthopaedic Surgery, Toho University over a 15 year period between 1961 and 1976 were analyzed. Accurate clinical records and histological findings were available in 91 patients, 80 of whom had benign tumors and 11 of whom had malignant ones. Recurrence was seen in 7 of the 80 patients with benign tumors. The prognosis was poor in those with malignant tumors as expected, especially in those with rhabdomyosarcoma.

Malignant pheochromocytoma arising in the organ of Zuckerkandl--a clinicopathological study

An autopsy case of malignant pheochromocytoma arising in the organ of Zuckerkandl is reported, of which distant metastases were found in the liver and lymph nodes. The biochemical and electron microscopic findings from the tumor tissue showed noradrenaline-secreting type. It was revealed that sex ratio in malignant pheochromocytoma was more prominent in the female, and the frequency of extra-adrenal origin was higher in malignant pheochromocytoma than in benign one from comparative study of reported cases of malignant pheochromocytoma.

The long-term prognosis infantile spasms--the present condition of cases of infantile spasms followed in school age

A follow-up study has been made of 25 cases with infantile spasms, all of whom were six years old or more at review. Only four (16%) out of 25 cases made a full recovery and attended normal school. Spasms ceased in 96% of all cases, but fits other than spasms (grand mal, tonic seizure, atonic seizure, myoclonic seizure, atypical absence and psychomotor seizure) occurred subsequently in 11 cases (44%). The EEG became normal in two cases (8%), but still showed modified hypsarhythmia in three cases (12%), "epileptic non-hypsarhythmic" discharges in 17 cases (68%) and non-specific abnormalities in three cases (12%). The important factors associated with good prognosis were normal development before the onset of spasms, late onset (seven months old or over) and short duration of spasms, the absence of other types of fit following spasms and lack of neurological abnormality. A bad prognosis was associated with abnormal development prior to the onset of spasms, early onset and long duration of spasms, the presence of other types of fit following spasms and evidence of any neyrological abnormality This follow-up may confirm that the therapy with ACTH-A has no significant effect on final mental state.