In Vitro Action of Matrix Metalloproteinases 2 and 9 Inhibitors on Na+/K+-ATPase, H+/K+-ATPase and PMCA Activities in the Osmoregulatory Epithelia of Climbing Perch (Anabas testudineus Bloch)

Matrix metalloproteinases 2 and 9 (MMP2 and MMP9) are involved in the extracellular matrix (ECM) remodeling. We tested the short-term in vitro action of inhibitors of MMP2 and MMP9 on P-type ion transporter function in organ explants of climbing perch (Anabas testudineus) to understand how these ECM remodeling components influence the ion transporter function in the osmoregulatory epithelia of fish. Graded doses (10^-8, 10^-7 and 10^-6 M) of inhibitors of MMP2 and MMP9 were administered in vitro to explants of gills, kidney and intestine, kept for either 15 or 30 min and the activities of P-type ATPase such as Na⁺/K⁺-ATPase (NKA), H⁺/K⁺-ATPase (HKA) and plasma membrane Ca²⁺-ATPase (PMCA) were quantified. We found that the inhibitors of MMP2 and MMP9 produced dose- and time-dependent modulation in the activities of NKA, HKA and PMCA in the tested tissue explants. Incubation of MMP2 and 9 inhibitors at the highest dose (10^-6 M) for 15 and 30 min produced substantial rise in NKA activity. Likewise, HKA activity that showed significant rise after incubation of 10^-7 and 10^-8 M inhibitors in gills and kidney explants, decreased at the lowest dose (10-8 M) of inhibitors. The lower doses of both inhibitors, while increasing PMCA activity in kidney and intestinal explants inhibited its activity in gill explant. These differential tissue-responsive actions of MMP2 and MMP9 inhibitors indicate that these ECM remodeling components can modify the function of the membrane-bound P-type ion transporters in the osmoregulatory tissues of fish.