Thiazides and loop diuretics both have opposite action on which of the following ions -

Ans. is 'c' i.e., Calcium Furosemide action on calcium* Furosemide increases Ca2+ excretion (contrast thiazides which reduce it) as well as Mg2+ excretion by abolishing transepithelial potential difference in the thick AscLH which drives reabsorption of these divalent cations.Thiazides action on calcium* By their action to reduce blood volume, as well as intrarenal haemodynamic changes, they tend to reduce g.f.r. This is one reason why thiazides are not effective in patients with low g.f.r. They decrease renal Ca2+ excretion and increase Mg2+ excretion by a direct distal tubular action.