<b>Isoproterenol (beta-adrenergic agonist) induces chloride ion secretion from the glands of frog skin</b>

Background: The study focused on the glandular epithelium, an essential part of the frog's skin that contains receptors for various chemicals. These glands include mucosal, serosal–mucous, and poisonous types. The serosal–mucous glands have alpha-adrenergic, beta-adrenergic, and muscarinic receptors, which respond to specific chemical stimuli by secreting ions. Aims and Objectives: This study aimed to determine the effect of Isoproterenol, a beta-adrenergic agonist at a concentration of 100 nM, on ionic transport in glandular epithelial tissues. The objectives included: 1) investigating the basic ionic transport under resting conditions, 2) examining the role of Isoproterenol in both the presence and absence of sodium and chloride ions in the experimental bathing conditions, and 3) comparing the effects of Isoproterenol with those of Forskolin on ionic transport. Materials and Methods: We employed a modified Ussing chamber, a device designed to measure ionic transport as Short Circuit Current (SCC), utilizing silver electrodes linked to an integrated voltage clamp circuit. To investigate the specific ionic transport in frog skin glands, we used several solutions, including Normal Ringer (NR), Sodium-Free Ringer (Na-FR), and Chloride-Free Ringer (Cl-FR). We also compared the effects of Isoproterenol and Forskolin at a concentration of 10 µM. Result: The results indicated that the short-circuit current (SCC) was significantly higher when Isoproterenol was used (29 ± 6 µA/cm²) compared to Na-FR (9 ± 5 µA/cm²) and Cl-FR (13 ± 5 µA/cm²). Additionally, Forskolin increased the SCC to 68 ± 8 µA/cm², up from the control value of 42 ± 6 µA/cm². Conclusion: This study concluded that the presence of Na+ and Cl- is essential for activating the co-transporter. The mechanism of action for Isoproterenol and forskolin induces ionic transport through cAMP formation. The findings demonstrated that Isoproterenol enhances the activation of Na+−K+−2Cl− co-transporters located on the serosal membrane of acinar cells within glandular tissues. The Na+ that enters the cell exits through the Na+−K+−ATPase pump, while K+ exits through K+−ATP channels on the serosal membrane. Additionally, Cl− ions are secreted into the lumen via the cystic fibrosis transmembrane conductance regulator (CFTR) protein, in response to cAMP generated by the action of Isoproterenol and forskolin.