Hjemdahl P, Fredholm B B
Acta Physiol Scand. 1976 Feb;96(2):170-9. doi: 10.1111/j.1748-1716.1976.tb10186.x.
NA-stimulated lipolysis and cAMP formation in isolated rat fat cells is inhibited by acidosis. In the present report we have examined the quantitative relationship between lipolysis and cAMP formation at normal and reduced pH and the possible involvement of adenosine, an endogenous inhibitor of cAMP formation. Adenosine antagonized cAMP accumulation and to a considerably lower degree lipolysis, effects potentiated by acidosis. Theophylline, an antagonist of adenosine effects, stimulated lipolysis and cAMP-accumulation, and potentiated responses to NA. Adenosine deaminase (ADA) had theophylline-like effects. Acidosis inhibited lipolysis and cAMP accumulation induced by ADA and theophylline to a larger extent than those induced by NA. It is suggested that adenosine modulates fat cell cAMP production and may contribute to the antilipolytic effect of acidosis. There was a curvilinear relationship between cAMP elevation and glycerol production in fat cell suspensions, which was different at pH 7.4 and at pH 6.6. The amount of cAMP needed for half-maximal activation of lipolysis increased from 1.3 (pH 7.4) to 3.1 pMol X 10(-5) cells (pH 6.6). The maximal glycerol production was reduced from 1 300 to 900 nMol X 10(-5) cells. The antilipolytic effect of acidosis is apparently due partly to an inhibition of cAMP formation and partly to inhibition of subsequent step(s) in the activation sequence.
酸中毒可抑制去甲肾上腺素（NA）刺激的离体大鼠脂肪细胞中的脂肪分解和环磷酸腺苷（cAMP）生成。在本报告中，我们研究了正常pH和降低的pH条件下脂肪分解与cAMP生成之间的定量关系，以及内源性cAMP生成抑制剂腺苷可能的参与情况。腺苷可拮抗cAMP积累，并在相当程度上抑制脂肪分解，酸中毒可增强这些作用。茶碱是腺苷作用的拮抗剂，可刺激脂肪分解和cAMP积累，并增强对NA的反应。腺苷脱氨酶（ADA）具有类似茶碱的作用。酸中毒对ADA和茶碱诱导的脂肪分解和cAMP积累的抑制作用比对NA诱导的更大。提示腺苷可调节脂肪细胞cAMP的产生，并可能促成酸中毒的抗脂解作用。脂肪细胞悬液中cAMP升高与甘油生成之间呈曲线关系，在pH 7.4和pH 6.6时有所不同。脂肪分解半最大激活所需的cAMP量从1.3（pH 7.4）增加到3.1 pMol×10⁻⁵细胞（pH 6.6）。最大甘油生成量从1300 nMol×10⁻⁵细胞降至900 nMol×10⁻⁵细胞。酸中毒的抗脂解作用显然部分归因于对cAMP生成的抑制，部分归因于对激活序列后续步骤的抑制。
