Large dose of radiation causes sour taste and vomiting. Why?

It is? Because it flatly contradicts you.

“The epiethelial lining [of the gut]… undergoes constant renewal and so requires a rapid cell turnover.. It is this intrinisc property that is considered a key factor in the radiosensitivity of the tissue… It is not clear whether nausea and vomiting stem from effects on the periphery and subsequent stimulation of higher centres or whether these signs are entirely a response of the CNS.”

Can you please quote where it says that the immediate effects are **not **due loss of cells due to failure of division? Because chapter 3.4 flatly contradicts you. It says exactly what I said in my post, and what you have claimed is wrong.

So can you please provide a quote of where this work says that the immediate effects of nausea and vomiting are not due loss of cells due to failure of division?

I will admit, my education on this subject is 20 years out of date, and that article does indicate that the CNS might be responsible for early onset nausea, but it stops well short of stating that as a definite fact as you have done. Rather it says that the cause remains unknown, and that the cause I proposed may well be correct.

So unless you can provide another quote which state outright that early inset nausea is not caused by cell division failure in the GIT, I think you have debunked yourself.

GI cells contain roughly 80% of the bodies serotonin. When they die, they release their serotonin and the nervous system interprets this as mucosal irritation and triggers a vomiting response. It is this same rationale that causes the nausea and vomiting of chemotherapy.

It is also the reason why selective serotonin antagonists are powerful anti-emetics.