Negulescu P A, Reenstra W W, Machen T E
Department of Physiology-Anatomy, University of California, Berkeley 94720.
Am J Physiol. 1989 Feb;256(2 Pt 1):C241-51. doi: 10.1152/ajpcell.1989.256.2.C241.
The role of cytosolic free Ca (Cai) in stimulating acid production by the parietal cell in response to the secretagogues carbachol (carb), histamine (hist), and dibutyryl adenosine 3',5'-cyclic monophosphate plus 3-isobutyl-1-methylxanthine (DBcAMP + IBMX) was evaluated. Microfluorimetry with fura-2 was used to measure Cai in single parietal cells within intact rabbit gastric glands. Acid production was determined in parallel experiments by monitoring the accumulation of [14C]aminopyrine (AP) in suspensions of glands. Carb increased peak Cai levels to 1 microM in a dose-dependent manner [concentration for half-maximal response (K0.5) = 8 microM] that correlated well with the dose dependence of carb-stimulated AP accumulation (K0.5 = 18 microM). The Ca chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) was used to attenuate secretagogue-induced Cai increases. Incubating glands for 10 min with 1 and 10 microM BAPTA/AM caused resting Cai to decrease from 119 to 93 and 80 nM, respectively. BAPTA/AM, 1 and 10 microM, blocked carb-stimulated increases in Cai by 60 and 90% and AP accumulation by 50 and 90%. Hist, which increases cytosolic cAMP, caused small and relatively infrequent increases in Cai. Even so, hist-stimulated AP accumulation was inhibited 8 and 40% by 1 and 10 microM BAPTA. DBcAMP had no effect on Cai, and AP accumulation caused by DBcAMP was unaffected by the concentrations of BAPTA tested. These data suggest that carb requires an increase in Cai as a secretory signal. Hist also exhibited some Cai dependence, which may be attributable to either a small increase in Cai or the necessity of having a specific basal level of Cai. A Cai requirement for DBcAMP-stimulated acid secretion was not detected. Thus the parietal cell possesses both Ca-dependent and Ca-independent stimulatory pathways, and at least one secretagogue (hist) may utilize both pathways.
评估了胞质游离钙（Ca i）在壁细胞响应促分泌剂卡巴胆碱（carb）、组胺（hist）和二丁酰腺苷3'，5'-环一磷酸加3-异丁基-1-甲基黄嘌呤（DBcAMP + IBMX）刺激产酸过程中的作用。采用fura-2微荧光测定法测量完整兔胃腺中单个壁细胞内的Ca i。在平行实验中，通过监测腺体制剂中[14C]氨基比林（AP）的积累来测定产酸情况。Carb以剂量依赖方式将Ca i峰值水平提高到1 μM[半数最大反应浓度（K0.5） = 8 μM]，这与carb刺激的AP积累的剂量依赖性（K0.5 = 18 μM）密切相关。使用钙螯合剂1,2-双（2-氨基苯氧基）乙烷-N，N，N'，N'-四乙酸（BAPTA）来减弱促分泌剂诱导的Ca i升高。用1和10 μM BAPTA/AM孵育腺体10分钟，使静息Ca i分别从119 nM降至93 nM和80 nM。1和10 μM的BAPTA/AM分别使carb刺激的Ca i升高60%和90%，AP积累减少50%和90%。Hist增加胞质cAMP，导致Ca i出现小幅度且相对不频繁的升高。即便如此，1和10 μM BAPTA分别抑制hist刺激的AP积累8%和40%。DBcAMP对Ca i无影响，DBcAMP引起的AP积累不受所测试的BAPTA浓度影响。这些数据表明，carb需要Ca i升高作为分泌信号。Hist也表现出一定的Ca i依赖性，这可能归因于Ca i的小幅升高或维持特定基础Ca i水平的必要性。未检测到DBcAMP刺激的酸分泌对Ca i的需求。因此，壁细胞具有钙依赖性和非钙依赖性刺激途径，并且至少一种促分泌剂（hist）可能同时利用这两种途径。
