bilirubin question- world

[TexasTriathlete]

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The question is something like "if energy-dependent organic anion transport across the hepatocellular membrane is selectively inhibited, what would be the most likely result?"

The answer is that bilirubin excretion in the urine would be increased.

I don't understand this at all. The explanation they provide is no help. I am having a pretty ******ed day though, so it might just be something simple that I'm missing. But if someone could explain this to me on a 3rd-grade level, I would appreciate it.

 

[username456789]

I got that question like two days ago. Our school skipped over all that stuff entirely during our two years, so those questions usually get the better of me. This question's explanation sucked, and really didn't even address the specific issue (why exporting less bilirubin out of the liver results in more being pissed out).

I think the basic idea, based on the weak explanation, is:

Unconjugated bili = water insoluble, has to bind albumin in blood, can't piss it out
Conjugated bili = water soluble, you can piss it out

1. Liver takes up unconjugated bili (which was produced by hemolysis or whatnot) via a passive process.
2. Liver conjugates bili
3. Liver secretes conjugated bili into the intestines via an active process apparently (maybe that's common knowledge among people who were actually taught this stuff). Some gets **** out. Some goes back to the liver. A little gets pissed out.
4. If secretion is blocked, bilirubin backs up in the liver and enters circulation, so you've got an excess in your blood, which is filtered by the kidney and ends up in the urinal.

 

[MilkmanAl]

It's not common knowledge, as far as I'm aware. I guessed like crazy on that question. When in doubt about something involving bilirubin and blockage/transport inhibition, something to do with blood or pee is a safe answer choice.

 

[hartbot]

Guy's explanation makes sense.

It's hard to think like this in the minute thats alotted, but when you go back to the basics it makes sense- lipophilic molecules can cross cell membranes, whereas water soluble ones can only do so with energy expenditure.

That seems like a 6 step integration to me.

But the follow up question is how does this conjugated bilirubin get into the blood if it cant be leave the hepatocytes?

 

[golfman]

I think Goljan has a nice diagram about bilirubin in the 3rd edition and talks about this, although if I recall correctly I had to stare at it for a while to understand. And of course I've forgotten since then so I'm not of much help.

And I have my LAST comprehensive Pathology final tomorrow (Monday), so I won't have time to look up the answer and explain it. Why am I on SDN? Gotta get back to Path!!!!

 

[TexasTriathlete]

okay, so the organic anion they are talking about is the conjugated bili, and they're talking about how it leaves the liver.

I kept thinking about something not being able to enter the hepatocytes. I actually got the question right because I didn't read it carefully, and I thought it was talking about something else.

 

[Pegasus1731]

Got that same question today and had no idea! Glad I found this post!

 

[Sol Rosenberg]

This is just a "no key words" explanation of Dubin-Johnson or Rotor syndrome. So, as others have said, you can't transport conjugated bilirubin out of the liver and some of it gets excreted in the urine.