Hjemdahl P, Fredholm B B
Acta Physiol Scand. 1977 Nov;101(3):294-301. doi: 10.1111/j.1748-1716.1977.tb06011.x.
The possibility that acidosis inhibits lipolysis indirectly by causing ionic shifts or by favouring the accumulation of an inhibitor has been tested in isolated fat cells. Lipolysis induced by 3 muM noradrenaline (NA) was inhibited by 40-60% and that induced by 1 mM theophylline (THEO) by about 75% when the pH was reduced to 6.6. Lipolysis induced by NA + THEO was inhibited by 20-30%. Changing the concentration of Ca++ or Mg++ did not alter the degree of inhibition. Reducing the K+-ion concentration enhanced the inhibitory effect of low pH on lipolysis induced by NA or NA + THEO, whereas cyclic AMP accumulation was uninfluenced. Omitting glucose from the incubation medium caused a slight enhancement of pH-induced inhibition of lipolysis (from 60 to 70%, p less than 0.01). Reducing the concentration of albumin, which binds inhibitory substances such as FFA, reduced lipolysis more at normal than at reduced pH. At high FFA/albumin ratios (5 or above) lipolysis was similar at normal and reduced pH. The antilipolytic effect of decreased pH was equally pronounced in perifused fat cells, where inhibitory substances are not allowed to accumulate. Our results suggest that the antilipolytic effect of acidosis is mainly a direct effect of the increase in H+ ion concentration. The inhibitory effect of acidosis on various responses to beta-adrenoceptor stimulation may be caused by a decreased formation of cyclic AMP in turn caused directly by the decrease in pH.
酸中毒通过引起离子转移或促进抑制剂积累而间接抑制脂肪分解的可能性已在分离的脂肪细胞中得到验证。当pH降至6.6时，3 μM去甲肾上腺素（NA）诱导的脂肪分解被抑制40 - 60%，1 mM茶碱（THEO）诱导的脂肪分解被抑制约75%。NA + THEO诱导的脂肪分解被抑制20 - 30%。改变Ca++或Mg++的浓度并未改变抑制程度。降低K+离子浓度增强了低pH对NA或NA + THEO诱导的脂肪分解的抑制作用，而环磷酸腺苷（cAMP）的积累未受影响。从孵育培养基中省略葡萄糖导致pH诱导的脂肪分解抑制略有增强（从60%增至70%，p < 0.01）。降低结合游离脂肪酸（FFA）等抑制性物质的白蛋白浓度，在正常pH下比在降低的pH下对脂肪分解的抑制作用更大。在高FFA/白蛋白比率（5或以上）时，正常pH和降低的pH下脂肪分解相似。在不允许抑制性物质积累的灌流脂肪细胞中，降低pH的抗脂解作用同样明显。我们的结果表明，酸中毒的抗脂解作用主要是H+离子浓度增加的直接作用。酸中毒对β - 肾上腺素能受体刺激的各种反应的抑制作用可能是由pH降低直接导致的环磷酸腺苷形成减少引起的。
