Problems changing column attribute

Hi folks, I have been breaking my head over this.
I logg in as testuser via pgadmin.
I create a table as user 'testuser' added some columns, one of them for example is name: 'testcolumn' type: varchar length: 50
Now I'd like to change testcolumn's length to 60, as user 'testuser' I'm not allowed to change it and pgadmin tells me  that I don't have the rights to change relation pg_attribute.

If I change the length of  'testcolumn' from an admin account it works. Now I granted all priviliges for this table to user 'testuser' via the admin account, but still I cannot change the length if I log in with 'testuser'.

Is there any chance to grant some user (in my case 'testuser') the right to change attributes, without making him superuser?

Thanks St.