“What is the role of vasopressin?”

A nephrologist will talk about osmolality and aquaporins.

An intensivist might talk about its use as a pressor.

But, ask an evolutionary or social scientist and you might be surprised by the answer…

#MedTwitter #NephTwitter #NSMC

Arginine vasopressin (AVP), also known as antidiuretic hormone (ADH), is a short peptide hormone coded by ⒸⓎⒻⓆⓃⒸⓅⓇⒼ.

We have a similar peptide, ⒸⓎⒾⓆⓃⒸⓅⓁⒼ, floating around in our bodies.

Is this AVP, too?

Nope: it’s oxytocin.

Oxytocin & vasopressin are evolutionary cousins located side-by-side on human chromosome 20. Invertebrates have one hybrid copy. Tandem duplication in the common jawed vertebrate ancestor gave rise to our two gene copies.

Image from https://science.sciencemag.org/content/322/5903/900.

Shortly after this gene duplication, the vasopressin system began to take shape and refine its specialized function: osmoregulation.

Transition of early life from sea to freshwater to land came with significant changes in osmotic stress.

Image from https://www.npr.org/2010/07/05/127937070/the-human-edge-finding-our-inner-fish.

To adapt to terrestrialization, kidneys developed more sophisticated urine concentrating systems.
The amphibian urothelium (analogous to mammalian kidney collecting ducts) became sensitive to ADH. This allows them to live in wet or dry habitats.

Fig. from https://link.springer.com/article/10.1007%2Fs12020-012-9634-y

Thanks in part to ADH, kidneys can effectively concentrate urine to meet a range of homeostatic needs.

Or, in the words of Homer W. Smith…

(Read a reprint of his classic text here: https://anatomypubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ar.a.20017)

We typically think of oxytocin and vasopressin as having pretty distinct roles.

Vasopressin:
free water absorption in the kidney via V2R
vasoconstriction via V1aR & V1bR

Oxytocin:
myometrial contraction
milk letdown

Did you know they both also have roles in socialization?

Vasopressin and oxytocin signalling in the brain regulates social behaviour in many species.

In humans, genetic variants in these receptors (particularly in the V1a receptor, AVPR1A) appear to contribute to sociobehavioral diversity.

More on this here: https://science.sciencemag.org/content/322/5903/900

So, what is the role of vasopressin?

An evolutionary scientist will say its adaptations helped our transition from water to land.

A social scientist might say it helps us socialize.

I’d say: vasopressin has allowed us to become human.