Biomaterial Database

Reversal of the epinephrine stimulation of Cl- transport in bullfrog cornea by phorbol esters. 1989

P S Reinach, and C Thurman, and H E Bazan, and N G Bazan

Department of Ophthalmology, Washington University School of Medicine, St. Louis, MO 63110.

The effects of protein kinase C (PKC) stimulation with phorbol dibutyrate, PDBu, were determined on transepithelial net Cl- transport (Isc) across the isolated bullfrog cornea. Between 1 nM and 1 microM, PDBu had no effect on either the Isc or the conductance, gt, as well as the membrane voltage (Vsc) but it decreased the fractional apical membrane resistance (fR0). PDBu caused a dose-dependent decline and reversal of the stimulatory effect of the mixed alpha and beta adrenergic agonist, epinephrine, on the Isc. With 1 microM PDBu, 100 microM epinephrine decreased the Isc by 20% below its control value. As without PDBu, epinephrine decreased fR0 and depolarized the Vsc. Evidence that this reversal by PDBu stems from a selective stimulation of PKC is: (1) neither its vehicle nor the inactive phorbol analog, 4 alpha-phorbol didecanoate, PDD (1 microM), decreased either the fR0 or altered the stimulatory effect of epinephrine on the Isc. (2) After preincubation with 30 microM H-7, which inhibited PKC stimulation in subcellular membrane and cytosolic fractions of frog corneal epithelium, the stimulatory effect of epinephrine on the Isc was unchanged by 1 microM PDBu. Preincubation with PDBu completely inhibited the stimulatory effect of the beta adrenergic agonist, isoproterenol (10 microM), on the Isc but did not affect the stimulatory effect of 1 microM forskolin on the Isc, indicating that PKC stimulation results in uncoupling of adrenergic regulation of adenylate cyclase activity. Epinephrine did not reverse the Isc in corneas that were preincubated with either the alpha 2- -adrenergic antagonist, yohimbine (100 microM), or the general alpha adrenergic antagonist, phenoxybenzamine (100 microM). With yohimbine, epinephrine had no effect on the Isc whereas with phenoxybenzamine the stimulation by epinephrine was fully restored. These effects suggest that stimulation of PKC is dependent upon the stimulation of alpha 1-adrenergic receptors by epinephrine as well as the presence of PDBu. Reversal and stimulation of the Isc by epinephrine were both associated with a depolarization of the Vsc and similar decreases in fR0. These similar effects on fR0 suggest that PKC stimulation as well as alpha 2 adrenergic activation by epinephrine are associated with increases in basolateral membrane resistance.

UI	MeSH Term	Description	Entries
D011493	Protein Kinase C	An serine-threonine protein kinase that requires the presence of physiological concentrations of CALCIUM and membrane PHOSPHOLIPIDS. The additional presence of DIACYLGLYCEROLS markedly increases its sensitivity to both calcium and phospholipids. The sensitivity of the enzyme can also be increased by PHORBOL ESTERS and it is believed that protein kinase C is the receptor protein of tumor-promoting phorbol esters.	Calcium Phospholipid-Dependent Protein Kinase,Calcium-Activated Phospholipid-Dependent Kinase,PKC Serine-Threonine Kinase,Phospholipid-Sensitive Calcium-Dependent Protein Kinase,Protein Kinase M,Calcium Activated Phospholipid Dependent Kinase,Calcium Phospholipid Dependent Protein Kinase,PKC Serine Threonine Kinase,Phospholipid Sensitive Calcium Dependent Protein Kinase,Phospholipid-Dependent Kinase, Calcium-Activated,Serine-Threonine Kinase, PKC
D011892	Rana catesbeiana	A species of the family Ranidae (true frogs). The only anuran properly referred to by the common name "bullfrog", it is the largest native anuran in North America.	Bullfrog,Bullfrogs,Rana catesbeianas,catesbeiana, Rana
D002712	Chlorides	Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.	Chloride,Chloride Ion Level,Ion Level, Chloride,Level, Chloride Ion
D003315	Cornea	The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous CORNEAL EPITHELIUM; BOWMAN MEMBRANE; CORNEAL STROMA; DESCEMET MEMBRANE; and mesenchymal CORNEAL ENDOTHELIUM. It serves as the first refracting medium of the eye. It is structurally continuous with the SCLERA, avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the TRIGEMINAL NERVE via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed)	Corneas
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D004837	Epinephrine	The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS.	Adrenaline,4-(1-Hydroxy-2-(methylamino)ethyl)-1,2-benzenediol,Adrenaline Acid Tartrate,Adrenaline Bitartrate,Adrenaline Hydrochloride,Epifrin,Epinephrine Acetate,Epinephrine Bitartrate,Epinephrine Hydrochloride,Epinephrine Hydrogen Tartrate,Epitrate,Lyophrin,Medihaler-Epi,Acetate, Epinephrine
D004848	Epithelium	The layers of EPITHELIAL CELLS which cover the inner and outer surfaces of the cutaneous, mucus, and serous tissues and glands of the body.	Mesothelium,Epithelial Tissue,Mesothelial Tissue,Epithelial Tissues,Mesothelial Tissues,Tissue, Epithelial,Tissue, Mesothelial,Tissues, Epithelial,Tissues, Mesothelial
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001693	Biological Transport, Active	The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.	Active Transport,Uphill Transport,Active Biological Transport,Biologic Transport, Active,Transport, Active Biological,Active Biologic Transport,Transport, Active,Transport, Active Biologic,Transport, Uphill
D015240	Phorbol 12,13-Dibutyrate	A phorbol ester found in CROTON OIL which, in addition to being a potent skin tumor promoter, is also an effective activator of calcium-activated, phospholipid-dependent protein kinase (protein kinase C). Due to its activation of this enzyme, phorbol 12,13-dibutyrate profoundly affects many different biological systems.	Phorbol-12,13-Dibutyrate,12,13-Dibutyrate, Phorbol,Phorbol 12,13 Dibutyrate