氟对成骨细胞样细胞胞内钙和钙通道电流的影响

目的 :观察氟 (Fluoride,F-)对培养的成骨细胞样细胞胞内钙和钙通道电流的影响。方法 :应用Fura 2负载的成骨细胞样细胞 ,通过紫外荧光分光光度仪测定细胞内游离钙的浓度 ,同时应用全细胞膜片钳技术记录成骨细胞样细胞钙通道的变化。结果 :氟可引起成骨细胞样细胞胞内钙增高 ,尤以 10 0ng/mlF-最为明显 ,与对照组比较差异显著 (P <0 .0 5 )。应用全细胞膜片钳技术发现 2 5ng/mlF-即可引起成骨细胞样细胞钙通道开放 ,随着染F-剂量的增加 ,Ca2 +通道电流的幅值增大 (P <0 .0 1) ,且F-对Ca2 +通道电流的兴奋作用呈剂量依赖性 (r =0 .9914)。结论 :F-可引起成骨细胞样细胞钙通道开放 ,从而导致细胞胞内钙浓度的增加。     

Hydrogen sulfide inhibits L-type calcium currents depending upon the protein sulfhydryl state in rat cardiomyocytes

Hydrogen sulfide (H(2)S) is a novel gasotransmitter that inhibits L-type calcium currents (I (Ca, L)). However, the underlying molecular mechanisms are unclear. In particular, the targeting site in the L-type calcium channel where H(2)S functions remains unknown. The study was designed to investigate if the sulfhydryl group could be the possible targeting site in the L-type calcium channel in rat cardiomyocytes. Cardiac function was measured in isolated perfused rat hearts. The L-type calcium currents were recorded by using a whole cell voltage clamp technique on the isolated cardiomyocytes. The L-type calcium channel containing free sulfhydryl groups in H9C2 cells were measured by using Western blot. The results showed that sodium hydrosulfide (NaHS, an H(2)S donor) produced a negative inotropic effect on cardiac function, which could be partly inhibited by the oxidant sulfhydryl modifier diamide (DM). H(2)S donor inhibited the peak amplitude of I( Ca, L) in a concentration-dependent manner. However, dithiothreitol (DTT), a reducing sulfhydryl modifier markedly reversed the H(2)S donor-induced inhibition of I (Ca, L) in cardiomyocytes. In contrast, in the presence of DM, H(2)S donor could not alter cardiac function and L type calcium currents. After the isolated rat heart or the cardiomyocytes were treated with DTT, NaHS could markedly alter cardiac function and L-type calcium currents in cardiomyocytes. Furthermore, NaHS could decrease the functional free sulfhydryl group in the L-type Ca(2+) channel, which could be reversed by thiol reductant, either DTT or reduced glutathione. Therefore, our results suggest that H(2)S might inhibit L-type calcium currents depending on the sulfhydryl group in rat cardiomyocytes.     

不溶性钙盐离子积在磷及氢氟酸烧伤中毒救治中的参考作用

目的根据不溶性钙盐离子积计算,将血钙控制于正常水平,从而将血磷酸与氟控制在致死性浓度以下,达到解救磷与氢氟酸烧伤中毒目的。方法氢氟酸与黄磷于新西兰兔背部皮肤致致死性磷与氢氟酸烧伤,伤后动物分为：氢氟酸烧伤组（HF,n=10）;氢氟酸烧伤钙治疗组（HF-Ca,n=10）;磷烧伤组（P,n=12）与磷烧伤钙治疗组（P-Ca,n=12）,汽油烧伤对照组（G,n=12）。两治疗组均给予钙治疗以将血钙水平控制在正常水平以上,观测伤后死亡率与血氟、磷、血总钙、游离钙水平。结果氢氟酸烧伤组伤后血氟（1．15±0．12）×10^-4mol／L,动物死亡率100％;磷烧伤后血磷显著升高,动物死亡率75％;两组血游离钙均较正常显著降低（P〈0．05）,钙治疗将血钙维持于正常水平后,7d内动物死亡率降低至普通烧伤的30％水平。结论维持血钙于正常水平能够防治磷及氢氟酸烧伤致死性中毒,这一结果能够从不溶性盐离子积计算中加以解释。     

噪声习服对听觉损伤的保护作用机制探讨

目的:探讨噪声习服对听觉损伤的保护作用机制.方法:建立噪声习服实验动物模型.采用免疫组织化学、激光扫描共聚焦显微镜(LSCM)及图像分析等技术,定量研究噪声习服后毛细胞内纤维状肌动蛋白(F-actin)、钙调蛋白(CaM)、热休克蛋白70(HSP70)的表达及游离Ca2 浓度的变化.结果:噪声暴露后毛细胞中F-actin、CaM及HSP70的表达均呈增加趋势.与噪声损伤暴露组(H组)比较,噪声习服后损伤暴露组(CH组)中F-actin和HSP70的表达均明显增多,CaM的表达具有增加趋势.声暴露后毛细胞内游离Ca2 浓度升高,噪声损伤暴露组毛细胞内游离Ca2 浓度明显高于噪声习服组(C组)和习服后损伤暴露组.结论:噪声习服使毛细胞对于其后声刺激的保护性反应增强,毛细胞内细胞骨架系统的加强及胞内钙稳态的维持在噪声习服的保护机制中具有重要意义.     

Changes in the regulation of calcium metabolism and bone calcium content during growth in the absence of endogenous prolactin and during hyperprolactinemia: a longitudinal study in male and female Wistar rats

Since endogenous prolactin has been shown to enhance food consumption, calcium absorption, and bone calcium turnover in the pregnant rat, the role of endogenous prolactin in the regulation of calcium metabolism was investigated in 3-day balance studies of female Wistar rats from the age of 3 to 11 weeks. The study was divided into two parts. In part I, calcium metabolism in males and females was compared. In part II, 3-week old female rats were divided into 5 groups: (i) control animals receiving 0.9% NaCl; (ii) animals receiving 6 mg bromocriptine/kg/day (- PRLendo group); (iii) animals receiving 2.5 mg ovine prolactin/kg/day (+PRLexo); (iv) sham-operated animals receiving 0.9% NaCl, and (v) animals with two extra pituitaries implanted under the renal capsule, receiving 0.9% NaCl (AP group). Results showed that rapid growth occurred between 3 and 6 weeks with maximum fractional calcium absorption and calcium retention at 5 weeks of age in both sexes. The data also showed a physiological significance of endogenous prolactin in enhancing calcium absorption and retention in 5 week old rats. In an absence of prolactin, peak calcium absorption was delayed in 7-week old animals, and vertebral calcium content of 11-week old animals was reduced by 18%. Hyperprolactinemia in the AP group was found to enhance fractional calcium absorption and calcium retention at 7, 9, and 11 weeks and increased the femoral calcium content by 16%. It could be concluded that a physiological role of prolactin is the stimulation of calcium absorption and maintainance of bone calcium content during growth and development.     

Structure of acidic phospholipase A2 for the venom of Agkistrodon halys blomhoffii at 2.8 A resolution.

The crystal structure of acidic phospholipase A2 from the venom of Agkistrodon halys blomhoffii has been determined by molecular replacement methods based on the known structure of Crotalus atrox PLA2, a same group II enzyme. The overall structures, except the calcium-binding regions, are very similar to each other. A calcium ion is pentagonally ligated to two carboxylate oxygen atoms of Asp-49 and each carbonyl oxygen atoms of Tyr-28, Gly-30 and Ala-31. A reason why the former enzyme functions as monomeric form, while the latter one does as dimer, could be presumed by the structural comparison of these calcium-binding regions. Although Gly-32 is usually participated as a ligand in the coordination with calcium ion in group I PLA2, it is characteristically replaced to Ala-31 in the present structure, and thus the coordination geometry of calcium ion is rather different from the usually observed one.     

Effects of calcium availability on reproductive output of big brown bats

Reproduction is a period of high calcium demand in vertebrates; therefore, calcium deficiency can limit reproductive output in mammals. Nutritional analyses show that insects are a poor calcium source, suggesting that insectivorous species are more likely to be calcium deficient. During pregnancy, big brown bats Eptesicus fuscus consume between 8 and 18 times less calcium than they are estimated to require. To accommodate calcium demand during pregnancy, many mammals mobilize more calcium from the skeleton, and extensive bone loss has been observed in some bats during pregnancy. A conflict may arise between the female and developing embryo over allocation of limited calcium supplies, which could limit reproductive output with respect to offspring size, mass and number. The effects of calcium deficiency on these three factors were tested by providing pregnant captive big brown bats with either a calcium-deficient diet or a diet providing the daily calcium requirement, as estimated for pregnant big brown bats, from the time of capture until parturition. Neonates were compared between groups for size, mass and number per female, as were the effects of maternal mass and size on neonate mass and size. Maternal mass and litter mass were positively related for the calcium-deficient group, but not for the calcium-supplemented group. This suggests that there is some interaction between maternal mass and calcium availability, most likely due to the relationship between body mass and skeletal mass, and that calcium availability is limiting the overall biomass of young that a female can produce.     

Inhibition of calmodulin-dependent cyclic nucleotide phosphodiesterase by flunarizine, a calcium-entry blocker

It has been reported that flunarizine, classified as calcium entry-blockers, is a potent brain protective drug without any heart depressant effect, contrasting with other drugs in this group. This paper presents evidence that through a competitive antagonism against calmodulin, a major intracellular calcium receptor, flunarizine inhibits the calcium X calmodulin-activated phosphodiesterase activity of bovine brain, but not of heart, whereas other calcium-entry blockers and calmodulin antagonists inhibit to the same extent, the activation of the enzyme from the two sources. It could be suggested that some of pharmacological effects by flunarizine and its differences from other calcium-entry blockers may be explained by its interaction with calmodulin.     

Single‐cell functional analysis of parathyroid adenomas reveals distinct classes of calcium sensing behaviour in primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a common endocrine neoplastic disorder caused by a failure of calcium sensing secondary to tumour development in one or more of the parathyroid glands. Parathyroid adenomas are comprised of distinct cellular subpopulations of variable clonal status that exhibit differing degrees of calcium responsiveness. To gain a clearer understanding of the relationship among cellular identity, tumour composition and clinical biochemistry in PHPT, we developed a novel single cell platform for quantitative evaluation of calcium sensing behaviour in freshly resected human parathyroid tumour cells. Live‐cell intracellular calcium flux was visualized through Fluo‐4‐AM epifluorescence, followed by in situ immunofluorescence detection of the calcium sensing receptor (CASR), a central component in the extracellular calcium signalling pathway. The reactivity of individual parathyroid tumour cells to extracellular calcium stimulus was highly variable, with discrete kinetic response patterns observed both between and among parathyroid tumour samples. CASR abundance was not an obligate determinant of calcium responsiveness. Calcium EC50 values from a series of parathyroid adenomas revealed that the tumours segregated into two distinct categories. One group manifested a mean EC50 of 2.40 mM (95% CI: 2.37–2.41), closely aligned to the established normal range. The second group was less responsive to calcium stimulus, with a mean EC50 of 3.61 mM (95% CI: 3.45–3.95). This binary distribution indicates the existence of a previously unappreciated biochemical sub‐classification of PHPT tumours, possibly reflecting distinct etiological mechanisms. Recognition of quantitative differences in calcium sensing could have important implications for the clinical management of PHPT.     

奥卡西平对偏头痛大鼠三叉神经节神经元钙电流的影响*

目的:研究奥卡西平(Oxcarbazepine,OXC)对大鼠三叉神经节神经元钙电流的调控作用。方法:SD大鼠随机分为3组(n=8):生理盐水组(NS组),致炎剂组(IS组),OXC预防组。应用膜片钳技术,采用全细胞记录方式,观察OXC对偏头痛大鼠急性分离的三叉神经节的高电压激活钙电流(HVA-ICa)的调控作用。结果:OXC能够抑制钙电流,使钙电流的激活曲线向去极化方向移动,使钙电流的失活曲线向超级化方向移动。结论:OXC可能通过抑制钙离子进入细胞膜,来预防偏头痛的发作。同时OXC可能对外周神经系统及伤害感受的传入的兴奋性起到调控作用。     

Evaluation of the Content of Antimony,Arsenic, Bismuth,Selenium, Tellurium and Their Inorganic Forms in Commercially Baby Foods

The purpose of the investigation is to reveal the influence of dietary calcium on fluorosis-induced brain cell apoptosis in rat offspring, as well as the underlying molecular mechanism. Sprague–Dawley (SD) female rats were randomly divided into five groups: control group, fluoride group, low calcium, low calcium fluoride group, and high calcium fluoride group. SD male rats were used for breeding only. After 3 months, male and female rats were mated in a 1:1 ratio. Subsequently, 18-day-old gestation rats and 14- and 28-day-old rats were used as experimental subjects. We determined the blood/urine fluoride, the blood/urine calcium, the apoptosis in the hippocampus, and the expression levels of apoptosis-related genes, namely Bcl-2, caspase 12, and JNK. Blood or blood/urine fluoride levels and apoptotic cells were found significantly increased in fluorosis rat offspring as compared to controls. Furthermore, the Bcl-2 messenger RNA (mRNA) expression levels significantly decreased, and caspase 12 mRNA levels significantly increased in each age group as compared to controls. Compared with the fluoride group, the blood/urine fluoride content and apoptotic cells evidently decreased in the high calcium fluoride group, Bcl-2 mRNA expression significantly increased and caspase 12 mRNA expression significantly decreased in each age group. All results showed no gender difference. Based on these results, the molecular mechanisms of fluorosis-induced brain cell apoptosis in rat offspring may include the decrease in Bcl-2 mRNA expression level and increase in caspase 12 mRNA expression signaling pathways. High calcium intake could reverse these gene expression trends. By contrast, low calcium intake intensified the toxic effects of fluoride on brain cells.     

低钙透析液联合醋酸钙对血液透析患者高磷血症的影响

目的：研究低钙透析液联合醋酸钙治疗对血液透析患者血磷、血钙及甲状旁腺激素iPTH水平的影响。方法：将30例维持性血液透析患者随机分为试验组和对照组,在试验期间所有患者均低磷饮食,两组透析液钙浓度均为1．25mmol／L,试验组同时给予醋酸钙治疗,对照组不应用醋酸钙治疗,三个月后观察和比较两组患者的血钙、血磷及血iPTH水平的变化。结果：治疗前,两组各组血磷、血钙、血磷和血iPTH的水平比较差异均无统计学意义（P〉0．05）。治疗后,对照组血钙水平明显下降（P〈0．05）,血iPTH水平略上升但无统计学意义（P〉0．05）,血磷水平无显著变化（P〉0．05）;试验组血iPTH水平略下降（P〉0．05）,血钙水平无明显变化（P〉0．05）,但血磷明显下降（P〈0．05）;且试验组血磷水平较对照组明显下降（P〈0．05）,血钙水平显著高于对照组（P〈O．05）,但在正常范围内,两组血iPTH水平比较无统计学意义（P〉0．05）。结论：低钙透析液联合醋酸钙治疗可有效降低血液透析患者的血磷水平,且不会导致高钙血症的发生。     

Effect of increased calcium intake on cardiac and vascular Na(+)-K(+)-ATPase activity in oral contraceptive-treated female Sprague-Dawley rats

The present study aimed at investigating the influence of increased dietary calcium on Na(+)-K(+)-ATPase activity in heart and aorta of female Sprague-Dawley rats treated with oral contraceptive (OC) steroids. Rats were grouped as control (CR), OC-treated and OC+calcium-treated. OC-treated and OC+calcium-treated received a combination of OC steriods (ethinyloestradiol and norgestrel; ig). OC+calcium-treated rats were fed with 2.5% calcium diet, while OC-treated and CR groups were fed on 0.9% calcium diet. The activity of Na(+)-K(+)-ATPase in heart and aorta was significantly lower in OC-treated rats than those in the other groups. OC treatment caused significant increase in plasma glucose and significant decrease in plasma K+ as compared to control group. Decrease in Na(+)-K(+)-ATPase activity and plasma K+ was abrogated by increased calcium intake, while increase in plasma glucose was not normalized by calcium supplementation. Plasma levels of Na+, lipid peroxidation index and ascorbic acid were comparable among the three groups. These results showed that OC treatment could lead to impaired activity of cardiac and vascular Na(+)-K(+)-ATPase, possibly due to reduced plasma K+ level and these effects could be abolished by high calcium diet.     

Sulfur dioxide restores calcium homeostasis disturbance in rat with isoproterenol-induced myocardial injury

Backgrounds: sulfur dioxide (SO?) could relieve isoproterenol (ISO)-induced myocardial injury, while the mechanism is unclear. This study aims to explore whether the protective effect of SO? on ISO-induced myocardial injury was mediated by the restoration of calcium homeostasis disturbance in cardiomyocyte. Methods and results: Rats were randomly divided into four groups: ISO group, ISO+SO? group, control group and SO? group. Content of Ca2? in H9c2 cells was assayed using confocal microscope, and cardiac function parameters were measured by echocardiography. Plasma biochemical values and myocardial ultra-structure changes were measured. Meanwhile, the activity, protein and gene levels of sarcoplasmic reticulum Ca2? ATPase (SERCA), and protein and phosphorylation of phospholamban (PLN) were detected. We found SO? derivatives could restore the decreased cardiac function, the abnormal lactate dehydrogenase, creatine kinase, alpha-hydroxybutyrate dehydrogenase, potassium, calcium, blood urea nitrogen and the damaged myocardial ultra-structure in rats, and regulate the increased Ca2? content in H9c2 induced by ISO. In addition, compared with ISO group, the decreased activities, protein and mRNA level of SERCA, as well as the decreased protein phosphorylation level of PLN in myocardial tissues were increased in ISO+SO? group. Conclusion: SO? derivatives might relieve calcium overload in association with the upregulating expression of SERCA and p-PLN/PLN by myocardial tissues in rats with ISO-induced myocardial injury.     

琥珀酸对大鼠海马CA1区神经元电压依赖性钙电流的影响

目的：观察不同浓度的琥珀酸对大鼠海马CA1区神经元电压依赖性钙通道（voltage—dependent calcium channels,VDCC）电流的作用,初步探讨琥珀酸对神经元保护的电生理学基础。方法：采用传统全细胞膜片钳技术和制霉菌素（nystatin）穿孔膜片钳技术观察琥珀酸对海马CA1区神经元VDCC电流的影响。结果：不同浓度的琥珀酸（10^-6、10^-5、10^-4、10^-3、10^-2和10^-1mol·L^-1）在海马CA1区对低电压激活（low—voltage activated,LVA）钙通道电流未见任何影响,而对高电压激活（high—voltage activated,HVA）钙通道电流的抑制呈浓度依赖性。对照组HVA钙电流为580．05±17．32pA,分别给予10^-6、10^-5、10^-4、10^-3、10^-2和10^-1mol·L^-1。的琥珀酸后,HVA钙电流依次为563．74±16．65,517．99±15．24,444．66±13．26,405．32±19．11,269．03±9．96和86．41±3．25pA,同对照组相比差异有统计学意义（n=8,P〈0．01）。结论：琥珀酸能浓度依赖性地抑制HVA钙电流,而对LVA钙电流无影响。由此推测琥珀酸可能通过抑制HVA钙电流减少Ca^2＋内流而影响海马CA1区神经元的兴奋性,从而抑制癫痫的形成,其脑保护作用可能与此有关。     

Research on Intra-Operative Indocyanine Green Angiography of the Parathyroid for Predicting Postoperative Hypoparathyroidism: A Noninferior Randomized Controlled Trial

Objective: A noninferiority randomized controlled trial was undertaken to clarify whether the postoperative measurements of serum calcium and parathyroid hormone and oral supplementation of calcium and calcitriol could be omitted if patients had at least one well-perfused parathyroid gland evaluated by intra-operative indocyanine green (ICG) angiography.Methods: Patients with at least one parathyroid gland well-perfused by ICG angiography (ICG score >2) were randomized to the control group or test group. For the control group, oral calcium and calcitriol were systematically supplemented. For the test group, no oral calcium or calcitriol was supplemented to the patients. Levels of serum calcium and parathyroid hormone of patients on the first and 30th postoperative day were compared between the two groups.Results: Among all 68 selected patients, 56 patients had at least one well-perfused parathyroid gland evaluated by intra-operative ICG angiography. The 56 patients were randomized to the control group or test group. There were no statistically significant differences in the levels of serum calcium and parathyroid hormone between test group and control group on the first or 30th postoperative day.Conclusion: The postoperative measurements of serum calcium and parathyroid hormone and oral supplementation of calcium and calcitriol were evaluated as redundant, if patients had at least one well-perfused parathyroid gland evaluated by intra-operative ICG angiography.Abbreviations: ICG = indocyanine green; NIR = near infrared; POD = postoperative day; PTH = parathyroid hormone; SBR = signal background ratio     

Calcium oxalate and calcium phosphate capacities of cardiac sarcoplasmic reticulum

Both oxalate-supported and phosphate-supported calcium uptake by canine cardiac sarcoplasmic reticulum initially increase linearly with time but fall to a steady-state level within 20 min. The departure from linearity could be due to a decrease in influx or to an increase in efflux of calcium. Because Ca2+-ATPase activity is linear, a decrease in the influx of calcium is an unlikely cause of the non-linear calcium uptake curves. A possible cause of an increase in calcium efflux is rupture of the vesicles. This hypothesis was tested by investigating the amount of calcium which could be released upon addition of 5 mM EGTA. The amount of rapidly releasable calcium was zero until a threshold calcium uptake of about 4-6 mumol calcium oxalate or calcium phosphate per mg was reached. After that point the rapidly releasable calcium continued to increase with calcium oxalate to reach more than 23 mumol/mg, but stayed constant at about 0.7 mumol/mg for calcium phosphate. The rapidly releasable calcium was attributed to calcium oxalate or calcium phosphate crystals externalized by vesicle rupture. The differences in the amounts of rapidly releasable calcium were attributed to different kinetics of calcium phosphate and calcium oxalate dissolution. Addition of ryanodine caused a marked increase in the threshold for rapidly releasable calcium oxalate. Transmission electron micrographs showed that vesicles can become filled with calcium oxalate crystals, but the vesicles were heterogeneous with respect to their size and their sensitivity to ryanodine. These observations support the hypothesis that calcium oxalate and calcium phosphate capacities are limited by vesicle rupture and that ryanodine increases the capacity by closing a calcium channel in a subpopulation of vesicles that otherwise would not accumulate calcium.     

Effects of a single dose of menadione on the intestinal calcium absorption and associated variables

The effect of a single large dose of menadione on intestinal calcium absorption and associated variables was investigated in chicks fed a normal diet. The data show that 2.5 micro mol of menadione/kg of b.w. causes inhibition of calcium transfer from lumen-to-blood within 30 min. This effect seems to be related to oxidative stress provoked by menadione as judged by glutathione depletion and an increment in the total carbonyl group content produced at the same time. Two enzymes presumably involved in calcium transcellular movement, such as alkaline phosphatase, located in the brush border membrane, and Ca(2+)- pump ATPase, which sits in the basolateral membrane, were also inhibited. The enzyme inhibition could be due to alterations caused by the appearance of free hydroxyl groups, which are triggered by glutathione depletion. Addition of glutathione monoester to the duodenal loop caused reversion of the menadione effect on both intestinal calcium absorption and alkaline phosphatase activity. In conclusion, menadione shifts the balance of oxidative and reductive processes in the enterocyte towards oxidation causing deleterious effects on intestinal Ca(2+) absorption and associated variables, which could be prevented by administration of oral glutathione monoester.     

Protein kinase C interaction with calcium: a phospholipid-dependent process

The calcium-binding properties of calcium- and phospholipid-dependent protein kinase C (PKC) were investigated by equilibrium dialysis in the presence and the absence of phospholipids. Calcium binding to PKC displayed striking and unexpected behavior; the free proteins bound virtually no calcium at intracellular calcium concentrations and bound limited calcium (about 1 mol/mol of PKC) at 200 microM calcium. However, in the presence of membranes containing acidic phospholipids, PKC bound at least eight calcium ions per protein. The presence of 1 microM phorbol dibutyrate (PDBu) in the dialysis buffer had little effect on these calcium-binding properties. Analysis of PKC-calcium binding by gel filtration under equilibrium conditions gave similar results; only membrane-associated PKC bound significant amounts of calcium. Consequently, PKC is a member of what may be a large group of proteins that bind calcium in a phospholipid-dependent manner. The calcium concentrations needed to induce PKC-membrane binding were similar to those needed for calcium binding (about 40 microM calcium at the midpoint). However, the calcium concentration required for PKC-membrane binding was strongly influenced by the phosphatidylserine composition of the membranes. Membranes with higher percentages of phosphatidylserine required lower concentrations of calcium. These properties suggested that the calcium sites may be generated at the interface between PKC and the membrane. Calcium may function as a bridge between PKC and phospholipids. These studies also suggested that calcium-dependent PKC-membrane binding and PKC function could be regulated by a number of factors in addition to calcium levels and diacylglycerol content of the membrane.