An absorber tube for solar collectors is provided. The absorber tube comprises a metal tube for carrying and heating a heat transfer medium, a sleeve tube enclosing the metal tube for forming an annular space that can be evacuated, a first container disposed in the annular space and filled with protective gas, an outer ring, and a transition element enclosing the metal tube for sealing off the annular space. The first container includes an outlet opening closed by a closure material, which releases the outlet opening under external actuation for introducing the protective gas into the annular space. The external actuation is applied by an opening unit that is activated for releasing the outlet openings. The first container is fixed in the annular space by a retaining device, which is on the outer ring and/or on the transition element.