The long term objective of this program is to determine the consequences of hormone-cell interaction at the level of cAMP accumulation and cellular responses to altered levels of the cyclic nucleotide. In this proposal we will examine the state of cells (in terms of the cAMP system) under conditions approximating those found in vivo. To do that, we will define the activities of adenylate cyclase, cAMP elimination mechanisms, relative rates of desensitization, and the protein kinase activity ratios (as an index of cAMP action) in cells incubated under a variety of conditions. It is our contention that the """"""""basal"""""""" state, that is, incubation in the absence of hormone never exists in vivo. Thus, we will approximate the in vivo basal state by incubation with concentrations of hormone appropriate to the resting state in intact animals. In the case of the catecholamines, levels of 1- 3nM have been reported (1). We will also examine the parameters of cAMP metabolism and action under levels of stimulation approximating those found in vivo, which are rarely greater than EC50. The experiments proposed test the following hypotheses: (1) That the cells in vivo are in a continuous state of partial desensitization. (2) That desensitization is a functional useful entity in the control of cAMP levels in cells. (3) That cAMP elimination is under elaborate and finely tuned control in intact cells. In the present period of the program we have established the procedures, assays, and models required for the measurement of the components cited above in cells going through the transition from zero levels to extremely high concentrations of hormone. The new program, which will yield quantitation of what happens as cells go from a continuous, low level of stimulation to one slightly higher, will provide us with a much better understanding of hormone and drug actions as they obtain in the living state.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK026943-07
Application #
3228108
Study Section
Physiological Chemistry Study Section (PC)
Project Start
1980-07-01
Project End
1992-06-30
Budget Start
1989-07-01
Budget End
1992-06-30
Support Year
7
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Texas Health Science Center Houston
Department
Type
Overall Medical
DUNS #
City
Houston
State
TX
Country
United States
Zip Code
77225
Richardson, M D; Goka, T J; Barber, R et al. (1994) Growth of S49 wild type cells in 3 nM epinephrine increases cyclic AMP phosphodiesterase activity. Life Sci 54:863-75
Proll, M A; Clark, R B; Butcher, R W (1993) Beta 2-adrenergic receptor mutants reveal structural requirements for the desensitization observed with long-term epinephrine treatment. Mol Pharmacol 44:569-74
Barber, R; Goka, T J; Butcher, R W (1992) Positively cooperative cAMP phosphodiesterase attenuates cellular cAMP responses. Second Messengers Phosphoproteins 14:77-97
Proll, M A; Clark, R B; Goka, T J et al. (1992) Beta-adrenergic receptor levels and function after growth of S49 lymphoma cells in low concentrations of epinephrine. Mol Pharmacol 42:116-22
Proll, M A; Clark, R B (1991) Potent Gi-mediated inhibition of adenylyl cyclase by a phosphonate analog of monooleylphosphatidate. Mol Pharmacol 39:740-4
Barber, R; Goka, T J; Butcher, R W (1989) Growth of S49 cells in low concentrations of beta-adrenergic agonists causes desensitization. Mol Pharmacol 36:459-64