Inhibition of DNA synthesis by phorbol esters through protein kinase C in cultured rabbit aortic smooth muscle cells

In cultured rabbit aortic smooth muscle cells (SMC), 12-O-tetradecanoylphorbol-13-acetate (TPA) induced DNA synthesis in the presence of plasma-derived serum to a small extent, but inhibited markedly the rabbit whole blood serum (WBS)-, platelet-derived growth factor (PDGF)- and epidermal growth factor-induced DNA synthesis. Phorbol-12,13-dibutyrate (PDBu) mimicked this antiproliferative action of TPA, but 4 alpha-phorbol-12,13-didecanoate was inactive in this capacity. Prolonged treatment of the cells with PDBu caused the partial down-regulation of protein kinase C. In these protein kinase C-reduced cells, WBS still induced DNA synthesis, but TPA did not inhibit the WBS-induced DNA synthesis. We have previously shown that protein kinase C is involved at least partially in the PDGF-induced DNA synthesis in rabbit aortic SMC. The present results together with this earlier observation suggest that protein kinase C has not only a proliferative but also an antiproliferative action in rabbit aortic SMC.

Possible involvement of protein kinase C in platelet-derived growth factor-stimulated DNA synthesis in vascular smooth muscle cells

In cultured rabbit aortic vascular smooth muscle cells (VSMC), protein kinase C-activating phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and phorbol-12,13-dibutyrate (PDBu) stimulated DNA synthesis in the presence of 10% cell-free plasma-derived serum. This stimulation was half that shown by PDGF. 4 alpha-Phorbol-12,13-didecanoate, known to be inactive for protein kinase C, was without effect in stimulating DNA synthesis. Prolonged treatment of the cells with PDBu led to a marked decrease in protein kinase C. In the pDBu-treated cells, the TPA-stimulated DNA synthesis was completely abolished whereas the PDGF-stimulated DNA synthesis was decreased to about half that in the control cells. These results suggest that protein kinase C is involved in PDGF-stimulated proliferation of VSMC.

Development of a selective clean-up method using immobilized antibody and its application to HPLC and GC/MS determination of a carbacyclin derivative, CS-570, in plasma

Methods for the determination of CS-570, a chemically stable prostacyclin analogue, in plasma were developed by using an immobilized antibody column followed by fluorescence HPLC and GC/MS. The CS-570 antibody, obtained from rabbit plasma by giving CS-570-BSA for a few months, was coupled to Sepharose 4B and used as extraction phase for sample clean-up and extraction of the drug. A plasma sample was applied to this column, washed with water and the drug was eluted with 90% acetonitrile. 0.02% (w/v) 9-anthryldiazomethane (ADAM) was added to the extract to form a fluorescent derivative. The CS-570-ADAM adduct exhibited high sensitivity when applied to HPLC with fluorescence detection and column switching. The detection limit was 1 ng/mL when 1 mL of plasma was available. Additionally, a pentafluorobenzyltrimethylsilyl derivative of CS-570 showed excellent sensitivity when determined by capillary GC interfaced to negative ion chemical ionization MS using a stable isotope labelled analogue as an internal standard.

Acute idiopathic interstitial myocarditis: case report with special reference to morphological characteristics of giant cells

Necropsy findings of an acute fatal case of idiopathic interstitial myocarditis were reported. The patient was a 33 year old housewife who had acute cardiac failure on the sixteenth day after the onset of the disease. Necropsy showed important pathological changes confined to the heart. Both ventricles were affected by confluent granulomas with an ill defined patchy appearance. Histologically these lesions consisted of round cells, histiocytes, eosinophils and myogenic giant cells. The findings were compatible with those of interstitial myocarditis associated with a proliferation of giant cells. Both atriums were also affected to a minor extent, detectable only by histological examination. Electron microscopy and cytochemistry showed that most giant cells noted in the lesion showed myofibrils and primary lysosomes in the cytoplasm. Giant cells were positive for myoglobin. Though the macrophage origin of the giant cell in this disorder has been emphasised in a recent report, these cytological results suggest that giant cells observed in the cardiac granulomatous lesions of this case were mainly myogenic in origin.

Activation of protein kinase C by the action of 9,11-epithio-11,12-methano-thromboxane A2 (STA2), a stable analogue of thromboxane A2, in human platelets

Incubation of human washed platelets with 9,11-epithio-11, 12-methano-thromboxane A2 (STA2), a stable analogue of thromboxane A2, caused the activation of protein kinase C and myosin light chain (MLC) kinase to the same extents as those induced by thrombin as judged by measuring the phosphorylation of a 40-kilodalton protein and MLC, respectively. However, STA2 stimulated much less phosphoinositide turnover than thrombin. Furthermore, the doses of STA2 necessary for protein kinase C activation and phosphoinositide turnover were higher than those necessary for MLC kinase activation, although the doses of thrombin necessary for these three reactions were nearly the same. These results suggest that protein kinase C may be activated at the Ca2+ concentrations higher than those required for MLC kinase activation by the action of STA2, presumably due to the inability of this agonist to produce diacylglycerol in an amount enough to increase the affinity of the enzyme for Ca2+.

Pharmacokinetics and pharmacodynamics of captopril in patients undergoing continuous ambulatory peritoneal dialysis

Pharmacokinetics and pharmacodynamics of captopril were studied in 5 continuous ambulatory peritoneal dialysis (CAPD) patients (including 2 hypertensive patients) after single oral administration of 50 mg captopril. The pharmacokinetic parameters for plasma free unchanged captopril were time to maximal concentration 1.1 +/- 0.3 h, maximal plasma concentration 387 +/- 75 ng X ml-1, elimination half-life 1.0 +/- 0.3 h, and the area under the concentration-time curve 711 +/- 144 ng X h X ml-1. For plasma total captopril (the sum of free unchanged captopril and its disulfide compounds) the values were time to maximal concentration 3.5 +/- 0.6 h and maximal plasma concentration 2,777 +/- 429 ng X ml-1. Captopril was detected in the dialysis fluid in all CAPD patients. Blood pressures in the 2 hypertensive CAPD patients were lower at 24 h after than before captopril administration. These results suggest that captopril may be eliminated by CAPD. In addition, there is a possibility that the antihypertensive effects of captopril may be prolonged in hypertensive CAPD patients.

Determination of immunoreactive antiarrhythmic peptide (AAP) in rats

A sensitive and specific radioimmunoassay for antiarrhythmic peptide (AAP) has been developed, utilizing 3-(4-hydroxy, 5-[125I]iodophenyl)propionyl AAP and guinea pig anti-AAP serum. Synthetic AAP was used as a standard and the polyethylene glycol method was employed to separate free AAP from antibody-bound AAP. The minimum detectable dose of AAP was 0.2 pmol. In the assay system, immunoreactivity was shown not to be attributable to fragments derived from AAP, gelatin or collagen peptides, which sequences differ only by one amino acid from those of AAP. Immunoreactive (IR) AAP extracted from rat tissues and serum gave parallel dose-response curves to those of AAP. Thus, the AAP equivalents per g or ml of tissues measured in adult male rats were 203 pmol in heart, 166 pmol in kidney, 4 pmol in serum, and 2 to 6 pmol in the other tissues. IR-AAP was separated into two fractions by Sephadex G-25 chromatography. Fr. I was considered to have a larger molecular mass than AAP, while Fr. II appeared to have a molecular mass equal to AAP. Ratios of Fr. II in total IR-AAP were 50% in heart and 10% in kidney, while serum IR-AAP gave only Fr. II. The IR-AAP level in heart showed a positive correlation increase with age in rats.

Comparison of the modes of action of Ca2+ ionophore A23187 and thrombin in protein kinase C activation in human platelets

In human platelets, the Ca2+ ionophore A23187 stimulated the phosphorylation of a 40 kDa protein and myosin light chain (MLC) to the same extents as those induced by thrombin, but the doses of A23187 for 40 kDa protein phosphorylation were higher than those for MLC phosphorylation, although the doses of thrombin for both reactions were nearly the same. Moreover, A23187 produced much less diacylglycerol than thrombin. However, the sites of the 40 kDa protein phosphorylated by the action of A23187 and thrombin were identical, and the 40 kDa protein phosphorylation induced by A23187 and thrombin was inhibited by tetracaine, an inhibitor for protein kinase C. Neither A23187 nor thrombin induced the production of a catalytic fragment of protein kinase C which might be generated by limited proteolysis with Ca2+-dependent protease. These results indicate that A23187 induces protein kinase C activation which phosphorylates the 40 kDa protein, but higher doses of A23187 are required for the activation of this enzyme than for the activation of MLC kinase.

Induction of protein kinase C activation and Ca2+ mobilization by fibroblast growth factor in Swiss 3T3 cells

Addition of fibroblast growth factor (FGF) to quiescent cultures of Swiss 3T3 cells rapidly induced diacylglycerol formation, protein kinase C activation and Ca2+ mobilization. Protein kinase C-activating agents such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and 1-oleoyl-2-acetylglycerol (OAG) mimicked the action of FGF and stimulated DNA synthesis in the presence of insulin. Prolonged treatment of the cells with phorbol-12,13-dibutyrate (PDBu) led to the down-regulation and complete disappearance of protein kinase C. In these cells, TPA and OAG did not induce DNA synthesis any more. FGF still elicited Ca2+ mobilization and DNA synthesis, but the magnitude of DNA synthesis was reduced to almost half as compared with that in the control cells. These results clearly indicate that both diacylglycerol and Ca2+ may serve as second messengers for FGF and suggest that these messengers may be involved in the mitogenic action of this growth factor.

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.