Subject: Can anyone describe how the drug Phenamil causes erthrocytes to lyse?

I'm currently analysing the results of my experiment involving the effect of 
varying concentrations of the amiloride analogue Phenamil* on mammalian red 
blood cells over time.

The results showed increased absorbance with a bench-top spectrophotometer (at 
595nm), denoting the lysis of the cell and the susequent release of the 
haemoglobin.

What I cannot figure out is the reason why....

from current information I can determine that it blocks epithelial-type Na+ 
channels, but does not inhibit Na+ pumps, (such as K+/Na+ or H+/Na+ pumps).

If the Na+ channels were blocked then the ion concentration in the cell would 
fall, causing cellular water concentrations to rise in relation to the medium - 
thus causing water to flow out of the cell (down the conc. gradient) and the 
cell would shrivel and not lyse!  Water flowing into the cell could only occur 
if the ion concentration increased, causing a low water concentration in the 
cell in relation to the medium.

Have I got this totally wrong??

HELP!

David Colwill

PS - Is anyone aware of any clinical uses of this drug?


*(3,5-diamino-6-chloro-N-[imino(phenylamino)methyl]-pyrazinecarboxamide)

Re: Can anyone describe how the drug Phenamil causes erthrocytes to lyse?