Is it possible to change ownership of a record using IOrganizationService.Update

Is there a way to set ownership (assign) a record as part of Updating an entity via the IOrganizationService.Update(...) method? The only way I have been able to do this is via an "AssignRequest" message.

For updating an entity this means 2 service calls, one for updating the fields and one for updating the ownership. Is there a way to perform the entire operation via a single call to IOrganizationService.Update(...) ?

-Abhijeet