Some of his most valued work, however, involves the central role of the ATPase in sodium transport in hypertension.
It long had been known that steroid-like compounds like ouabain and digitoxin (both derived from plants) could block the Na,K-ATPase and, thus, force increased heart contractions, a fact that was used to develop similar compounds as treatments for congestive heart failure (though they are no longer widely used, as better drugs such as angiotensin-converting enzyme (ACE) inhibitors have come along).
Out of Focus: A Little Less Conversation, A Little More Science
Jerry Lingrel’s sabbatical with John Gurdon at the MRC laboratory was a fantastic experience, although it did take a while to adjust to local customs. “The scientists there loved to socialize,” he says. “They talked over morning coffee, lunch and afternoon tea.” At first, Lingrel didn’t join the fun – “I thought I was here to work not talk”— but he eventually got hooked. “I had so much fun talking to all the great scientific minds at the MRC about ideas and techniques, and soon I understood why experiments never seemed to fail there.” However, Lingrel ended up becoming such the social butterfly during the day that he had to come back to lab every night to do the actual experiments.
However, some controversy also developed, as evidence seemed to suggest that animals produced their own ouabain-like steroids to modulate Na,K-ATPase activity (so-called endogenous ouabains). As Lingrel notes, while several studies had shown the presence of ouabain in normal blood samples, it was extremely difficult to prove that they had been synthesized in the body. “And, from a logical standpoint, people wondered why the human body would want to synthesize ouabain, which is a toxic molecule,” Lingrel says.
On the other hand, comparative work done by Lingrel’s team found that the binding site for ouabain and similar drugs in the Na,K-ATPase α subunit was heavily conserved from fruit flies to humans, which would support a physiological role, and, by extrapolation, a physiological ligand.
“So, we decided to work on this mystery, but, rather than focus on the compounds, we decided to focus on the binding site.” His reasoning was based on the interesting observation that one of the four mouse α subunit isoforms (α1) happened to be resistant to ouabain. So, he mutated two amino acids in the α2 isoform (the major vascular form), so it resembled α1 in one group of mice and altered α1 so it resembled α2 in another group. He then induced stress in the mice to see what happened.
“Sure enough, the mice that contained the mutated α2 were resistant to hypertension,” Lingrel says, “whereas the animals that had the altered α1 almost blew up because they became so hypertensive.” That seemed to confirm that the ouabain binding site was physiologically important in regulating blood pressure, and something in the blood was interacting with it. Lingrel is currently collaborating with some colleagues at the University of Cincinnati to try to find that elusive endogenous ligand.