Endogenous signalling system involved in parotid gland adenosine A(1) receptor-amylase release.
OBJECTIVE
In this study, we have determined signalling pathways involved in adenosine A(1) receptor (A(1) receptor)-dependent stimulation of amylase release in rat parotid gland.


METHODS
Amylase release, binding and cyclic adenosine monophosphate (cAMP) assays, inositol phosphates (IPs) production and nitric oxide synthase (NOS) activity in the presence of cyclopentyl-1,3-dipropylxanthine (CPA) alone or in the presence of different inhibitory drugs were performed.


RESULTS
The binding parameters of specific A(1) antagonist [(3)H]-cyclopentyl 1,3-dipropilxanthine ([(3)H]-DPCPX) in parotid gland membranes show a population of high affinity sites with K(d) (nm) 0.53 +/- 0.06 and B(max) (fmol mg(-1) protein) 122.6 +/- 10.2. CPA stimulation of A(1) receptor exerts an increase in amylase release, IPs accumulation, cAMP production and NOS activity. All these A(1) agonist effects were blocked by the A(1) receptor antagonist DPCPX. Inhibitors of phospholipase C (PLC), calcium/calmodulin (CaM), protein kinase C (PKC), and adenylate cyclase, but not NOS, activities attenuated the CPA stimulatory effect on amylase release. The effect of CPA on amylase release significantly correlated with its action either on cAMP or on IPs accumulation.


CONCLUSIONS
These results suggest that CPA activation of parotid gland A(1) receptor induces a stimulatory effect on amylase release associated with increased production of cAMP and IPs accumulation. The mechanism appears to occur secondarily to stimulation of phosphoinositide turnover via PLC activation. This, in turn, triggers cascade reactions involving CaM and PKC. The CPA stimulation of NOS does not appear to participate in amylase release.
Finkelberg
A
A
Physiology Unit, School of Dentistry, Córdoba National University, Buenos Aires, Argentina.
Busch
L
L
Reina
S
S
Sterin-Borda
L
L
Borda
E
E
D058916:Adenosine A1 Receptor Antagonists; D000681:Amylases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000032:analysis; D005260:Female; D007295:Inositol Phosphates / Q000032:analysis; D019001:Nitric Oxide Synthase / Q000378:metabolism; D010306:Parotid Gland / Q000201:enzymology / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D043682:Receptor, Adenosine A1 / Q000502:physiology*; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014970:Xanthines / Q000378:metabolism
D058916:Adenosine A1 Receptor Antagonists; D007295:Inositol Phosphates; D043682:Receptor, Adenosine A1; D018047:Receptors, Purinergic P1; D014970:Xanthines; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D000681:Amylases; D002118:Calcium