Lipid metabolic interrelationships and phospholipase activity in gustatory epithelium of Ictalurus punctatus in vitro.
Lipid metabolic interrelationships and phospholipase activity in gustatory epithelium of Ictalurus punctatus in vitro.
复制标题
体外斑点叉尾鱼味觉上皮细胞脂质代谢相互关系和磷脂酶活性。
作者：
Rabinowitz,JL;Huque,T;Brand,JG;Bayley,DL
斑点叉尾（Ictalurus punctatus）是研究味觉外周生化机制的重要模型。该组织内脂质的类型、量和代谢活性通过形成其中包埋味觉刺激物的受体的基质并通过充当第二信使的前体而在味觉传导中起重要作用。本文报道了这种动物味觉器官（触须）上脂质之间的代谢相互转换。当[32 P]磷酸钠与来自I. punctatus，磷脂被标记。溶血磷脂酰胆碱（LPC），磷脂酰胆碱（PC）和磷脂酰肌醇（PI）的最大掺入发生在20分钟左右。磷脂酰乙醇胺（PE）和磷脂酰丝氨酸（PS）标记较慢。LPC和PC中的标记从20 min至120 min下降，而其他级分的标记在20 - 120 min时间段内增加或稳定。向培养基中加入1，2-二-[1 ′-14 C]棕榈酰-sn-甘油-3-磷酸胆碱后，在几分钟内在所有测定的磷脂中发现14 C。掺入的标签的量随时间的推移而增加，最大标记的所有磷脂发生在15分钟。然而，14 C主要出现在第一（5分钟）在中性脂质部分（部分AG，由游离脂肪酸，甘油单酯和甘油二酯，甘油三酯和甲酯），然后迅速下降，磷脂逐渐纳入更多的标签。在加入1-[1 ′-14 C]棕榈酰-sn-甘油-3-磷酸胆碱（溶血磷脂酰胆碱）的几分钟内，在中性脂质组分AG中检测到14 C标记，然后在PC组分中检测到14 C标记，随后在其他磷脂中检测到14 C标记。PC馏分最大标记40分钟。使用适当的放射性标记的底物，溶血磷脂酰胆碱磷脂酶A1和磷脂酰胆碱磷脂酶D的活动在该组织中进行了检测。观察到磷脂酰胆碱磷脂酶A2的活性非常低。实验结果表明，该动物味觉器官中存在着活跃而快速的磷脂交换、降解、合成和清除途径，提示磷脂酶A1和D型活性是导致LPC和PC快速降解的主要原因。
The catfish,Ictalurus punctatus, is an important model for studying the biochemical mechanisms of taste at the peripheral level. The type, amount and metabolic activity of the lipids within this tissue play important roles in taste transduction by forming the matrix in which the receptors for taste stimuli are imbedded and by acting as precursors to second messengers. The metabolic interconversions that occur among the lipids on the taste organ (barbels) of this animal are reported here. When sodium [32P]phosphate was incubated with minced pieces of epithelium from the taste organ ofI. punctatus, phospholipids became labeled. Maximal incorporation occurred near 20 min for lysophosphatidylcholines (LPC),phosphatidylcholines(PC) and phosphatidylinositols (PI). The phosphatidylethanolamines (PE) and phosphatidylserines (PS) became labeled more slowly. The label in LPC and PC declined from 20 min to 120 min, while that of the other fractions increased or was stable over the 20–120 min time period. Upon addition of 1,2-di-[1′-14C]palmitoyl-sn-glycero-3-phosphocholine to the medium,14C was found within minutes in all of the phospholipids assayed. The amount of label incorporated increased with time, with maximum labeling for all phospholipids occurring at 15 min. However,14C appeared predominantly first (by 5 min) in a neutral lipid fraction (fraction AG, consisting of free fatty acids, mono- and diglycerides, triglycerides and methyl esters), then declined rapidly as the phospholipids gradually incorporated more label. Within minutes of addition of 1-[1′-14C]palmitoyl-sn-glycero-3-phosphocholine (lysophosphatidylcholine) the14C-label was detected in the neutral lipid fraction AG, then in the PC fraction, and later in the other phospholipids. The PC fraction was maximally labeled by 40 min.Using the appropriate radiolabeled substrates, lysophosphatidylcholine phospholipase A1and phosphatidylcholine phospholipase D activities were detected in this tissue. Very low activity of a phosphatidylcholine phospholipase A2was observed. The experiments indicate that there are active and rapid exchange, degradation, synthesis and scavenger pathways of phospholipids in the taste organ of this animal, and suggest that phospholipases A1and D-type activities are primarily responsible for the rapid breakdown of LPC and PC.