phospholipase C, PC phospholipase D, PA phos- 
phohydrolase, and DAG kinase are being defined in 
rat liver. 
A sensitive method for the measurement of PA in 
tissues has been developed and used to determine 
the changes in PA in regenerating liver after partial 
hepatectomy. This lipid increases significantly 0.5 h 
after surgery and reaches a maximum value at 
1.5 h. In contrast, DAG increases maximally at 0.5 h 
..and then declines. These early changes in DAG and 
PA may play signaling roles in the acceleration of 
growth after hepatectomy 
A protein kinase that is stimulated by PA has been 
identified in rat liver cytosol. It selectively catalyzes 
the phosphorylation of 33 and 35 kDa proteins and 
also some of higher and lower weights. The stimu- 
lation by PA depends on Ca^"*" in the submicromolar 
(i.e., cytosolic) range and is not mimicked by other 
PUBLICATIONS 
lipids, including DAG in combination with phos- 
phatidylserine; i.e., it does not involve protein ki- 
nase C. The PA-stimulated kinase is active toward 
histone 1, histone lA, and myelin basic protein. 
When tested against the specific peptide substrates 
of known protein kinases, it is most active toward a 
peptide of the S6 ribosomal protein but causes lit- 
tle phosphorylation of the peptide substrates of 
cAMP-dependent protein kinase, cGMP-dependent 
protein kinase, Ca^^-calmodulin-dependent pro- 
tein kinase II, protein kinase C, and several protein 
tyrosine kinases. The PA-stimulated protein kinase 
is being purified to homogeneity It may be an im- 
portant mediator of the cellular effects of PA. 
Dr. Exton is also Professor of Molecular Physiol- 
ogy and Biophysics and of Pharmacology at 
Vanderbilt University School of Medicine. 
Books and Chapters of Books 
Blackmore, RE, Lynch, C.J., Bocckino, S.B., and Exton, J.H. 1989. Regulation of hepatic glycogenolysis by cal- 
cium-mobilizing hormones. In Cell Calcium Metabolism: Physiology, Biochemistry, Pharmacology, and 
Clinical Implications (Eiskum, G., Ed.). New York: Plenum, pp 179-185. 
Exton, J.H. 1988. Mechanisms of action of glucagon. \nNew Comprehensive Biochemistry. II. Hormones and 
Their Actions (Cooke, B.A., King, R.J.B., and VanDer Molen, H.J., Eds.). Amsterdam: Elsevier Science, vol 
18B, pp 231-264. 
Articles 
Augert, G., Blackmore, P.F., and Exton, J.H. 1989- Changes in the concentration and fatty acid composition of 
phosphoinositides induced by hormones in hepatocytes. J Biol Chem 264:2574-2580. 
Blackmore, PP., and Exton, J.H. 1989. Ca^"*" fluxes and phosphoinositides in hepatocytes. Methods Enzymol 
35:534-545. 
Bocckino, S.B., Wilson, RB., and Exton, J.H. 1989. An enzymatic assay for picomole levels of phosphatidate. 
Ann Biochem 180:24-27. 
Bouscarel, B., Blackmore, PP., and Exton, J.H. 1988. Characterization of the angiotensin II receptor in pri- 
mary cultures of rat hepatocytes. Evidence that a single population is coupled to two different responses. 
J Biol Chem 263:14913-14919. 
Bouscarel, B. , Wilson, PB. , Blackmore, RE. , Lynch, C.J. , and Exton, J.H. 1988. Agonist-induced down-regula- 
tion of the angiotensin II receptor in primary cultures of rat hepatocytes. J Biol Chem 263:14920-14924. 
Exton, J.H. 1988. The roles of calcium and phosphoinositides in the mechanisms of aj^-adrenergic and other 
agonists. Rev Physiol Biochem Pharmacol 111:117-224. 
Exton, J.H. , and Blackmore, EE. 1989- Calcium-mediated hormonal responses. Endocrinology 5:58-74. 
Lynch, C.J., Blackmore, PP. , Johnson, E.H., Wange, R.L., Krone, EK., and Exton, J.H. 1989. Guanine nucleo- 
tide binding regulatory proteins and adenylate cyclase in livers of streptozotocin- and BB/Wor-diabetic 
rats. Immunodetection of G^ and G, with antisera prepared against synthetic peptides. / Clin Invest 
83:2050-2062. 
Stewart, S.J., Prpic, V, Johns, J.A., Powers, ES., Graber, S.E., Eorbes, J.T., and Exton, J.H. 1989. Bacterial toxins 
affect early events of T lymphocyte activation. / Clin Invest 83:234-242. 
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